A color scheme is a range of related colors that can be applied to a collection of features, rasters, graphic elements, or symbol components. Color schemes contain at least two colors; the transition between pairs of colors can be either a continuous gradient or a discrete boundary with no blending from one color to another. Color schemes can also be random, in which a variety of colors residing between two defined colors in an HSV color space make up the scheme in a random order. Color schemes of differing types can be combined to make complex collections of colors called multipart color schemes. Color schemes can be stored in styles for reuse or sharing.
Color schemes can be modified in the Color Scheme Editor window. In the Symbology pane , on the Primary symbology tab , click the Color scheme drop-down menu and click Format color scheme.
When a color scheme is edited, a version of it is created and added to the Color scheme drop-down menu. You can choose any version of the color scheme to go back to those settings. The versions cannot be deleted manually, but all unused custom color scheme versions are deleted when the Symbology pane is closed or the primary symbology is changed.
Color schemes are called color ramps in ArcMap, ArcScene, and ArcGlobe.
Continuous color schemes
Continuous color schemes show a smooth gradation of two or more color stops. Each color stop is defined by a color, its transparency, and a position along the scheme defined as a percentage of the total scheme length from left to right. A stop is always located at each endpoint, at positions 0 percent and 100 percent; the color and transparency of these two stops can be changed, but their positions cannot. A stop is the specific point where the blending of two adjacent colors in a gradient ends. You can move stops by clicking them, even changing their relative positions by dragging one over the top and beyond another.
You can customize continuous color schemes. In the Color Scheme Editor window, click the Add color button to add a color stop to the color scheme, or click the Remove color button to remove the selected color stop. Click the Reverse color scheme button to reverse the order of all the stops. Check the Evenly distribute color stops check box to arrange all stops evenly along the length of the color scheme.
The segments between color stops also dictate the appearance of a color scheme. The selected segment is shown by a black bar to the left of the selected color stop. Color scheme segments have two properties: Algorithm determines the path traversed through the color space between the two stop colors (HSV or CIE Lab), and Polar Direction determines the direction traversed around the color wheel for variations in hue (shortest path or longest path).
Color space algorithms
The appearance of segments in a continuous color scheme is determined by the Algorithm property, which calculates the interim colors between the two surrounding color stops.
The HSV (hue, saturation, and value) algorithm is a linear traverse through the color space between value pairs: a linear path from the hue of color 1 to the hue of color 2, a linear path from the saturation of color 1 to the saturation of color 2, and a linear path from the value of color 1 to color 2. All intervening colors are shown, so it is not always the most suitable for quantitative rendering.
When a segment uses the HSV algorithm, the Polar Direction property dictates whether the path from the hue of color 1 to the hue of color 2 follows the shortest direction around the color wheel (the default), or the longest. Use the Polar Direction pull-down menu to make your choice. When one or both of the color stops on either end of the segment has no hue component (whites, grays, and blacks), the Polar Direction setting has no effect because there are no hues to blend. When a small hue value is present, some differentiation in color progression can be seen when changing the polar direction. For this reason, HSV color schemes that traverse through low-hue colors may appear differently from their color ramp counterparts in previous versions of ArcGIS.
The CIELab algorithm blends two colors without traversing intervening hue space, resulting in a smoother progression from color 1 to color 2 than the HSV algorithm produces. In many cases, this produces a smooth scheme between two colors, but intermediate color values can be gray (low saturation) if there is a great difference between the two colors. Polar Direction is unavailable for CIELab segments, since this algorithm always follows a direct path through the color space.
The Linear algorithm blends two colors with a linear traversal of the color channel values of color 1 and color 2. By not implying a color space to traverse, the algorithm works directly with the channel values of the specified colors. Use a linear ramp to interpolate between a smooth transition of raw color values for stops that are known to be perceptually equivalent steps. Polar Direction is unavailable for linear segments since the algorithm always follows a direct path through the color space.
Discrete color schemes
Discrete color schemes consist of two or more solid blocks of colors with no gradation between them. The blocks are synonymous with the color stops in continuous color schemes, but they have only color and transparency properties. There is no concept of a color scheme segment in discrete color schemes. You can rearrange the order of the blocks by clicking and dragging.
You can further customize discrete color schemes by adding and removing blocks or reversing the order of all blocks. In the Color Scheme Editor window, click the Add color button to add a color stop to the color scheme, or click the Remove color button to remove the selected color stop. Click the Reverse color scheme button to reverse the order of all the stops.
Random color schemes
Random color schemes do not contain color stops, segments, or blocks. They are defined solely by a minimum and a maximum HSV color. The scheme is compiled of discrete hues that are generated randomly so that their H (hue), S (saturation), and V (value) settings lie between the H, S, and V values of the minimum and maximum colors, respectively. A single transparency value is applied to the entire scheme. Random color schemes do not include any selectable components along the scheme preview. The appearance of the color scheme is dictated by the HSV values specified as minimums and maximums from two color pickers.
Random color schemes are regenerated each time they are opened or applied. In the Color Scheme Editor window, click the Regenerate button to manually form a new arrangement of random interim colors between the minimum and maximum values. This updates the seed value. If you find an arrangement you want to return to, note the seed value and reenter it when you apply the scheme.
To change the minimum and maximum colors, choose colors from the color picker or click More colors. Regardless of the native color model of the selected color, colors are converted to the HSV color space, and those respective values are used as the limits for all interim colors generated along the scheme.
Transparency does not vary along the length of the random color scheme; it is a single value applied to the entire scheme. The default transparency setting is 0 percent, which is fully opaque. Transparency is indicated visually in the scheme when an underlying gray checkerboard shows through.
Multipart color schemes
Multipart color schemes consist of any combination of two or more continuous or discrete subschemes. Subschemes are identical to their stand-alone counterparts, except that continuous color schemes in a multipart color scheme contain only two stops. A multipart color scheme can contain up to 20 subschemes but cannot contain another multipart color scheme.
In the Color Scheme Editor window, choose a subscheme type from the drop-down menu, and click Add to add it to the subschemes list. Click the Remove button to remove it from the list. You can reorder subschemes or add new subschemes at any time.
When a multipart color scheme includes two or more subschemes, the color scheme preview labels show the percentage weight of each subscheme. Click and drag the arrow left or right to change the percentages between two subschemes.
Click the Edit button to modify the subscheme's color settings. Click the back arrow to return to the whole scheme.
Continuous subschemes contain only two color stops, one at each extremity of the subscheme. The Add color button, Remove color button, and Position spinner control are not present in the continuous subscheme component. A multipart scheme that contains only continuous subschemes, in which each end color is equal to the subsequent start color, is converted to a continuous scheme when it is reopened.
Bivariate color schemes
Bivariate color schemes are designed for use with bivariate colors symbology. They combine the color values of two discrete color schemes to create a multiclass grid of colors. The size of the grid is always 2x2 ,3x3, or 4x4. Unlike discrete color schemes, bivariate color schemes can be rotated, but their sequential order cannot be rearranged dynamically. Individual colors can be edited.
To change one or more colors in a bivariate color scheme, in the Color Scheme Editor window, click a color cell. Under Settings, you can change the color or transparency value of that cell. You can also click the Rotate button to change the orientation of the color scheme 90 degrees, or click the Reset button to return the color scheme to its original settings. Click Save to a style to save the color scheme to a custom style.