Several of the coloring methods, including `Beta', `Charge', and `Occupancy', describe a range of floating point values rather than a set of names. These are colored via the color scale, which is a list of 1024 smoothly changing colors. There are many color gradations available. All of them consist of transformations of three colors. For instance, ``RGB'' colors the smallest value red, values near the middle of the scale are green, and the largest values are blue. Colors in-between are linear mixes of the two colors. The list of available gradations is given below.
The minimum of the range of values is linearly scaled and shifted to start at 0 and end at 1. Assume the color scale is RGB. For a given value of x in the scale range [0..1], the RGB value is found first from a linear scaling based on the midpoint. If x 0, R is 1 (for maximum red). This continues linearly until x midpoint, at which point, R is 0 and stays 0. The green component is 0 at both x 0 and x 1 and is 1 at the midpoint. Linear scaling occurs in between. The blue component is 0 for x midpoint, and 1 for x 1.
An additional term, ``min'', is added to each of the component terms before they are merged. This shifts the final colors more towards white or black. Min can take on values from -1 to 1.
There is only one color scale used at a time so it is impossible to display objects colored by multiple different color scales.