Under MapWindow's current, equal-increment coloring algorithm, the following two terrains would receive exactly the same three colors, thus obscuring the terrain differences:
Terraine A B
Slope 1 5 deg 80 deg
Slope 2 10 deg 85 deg
Slope 3 15 deg 90 deg
So it would be useful if MapWindow offered proportional coloring as an option.
(This would require, in addition, that the user be allowed to specify the top-of-scale value. In the case of percentages, this will always be 100. But in other cases some other top-of-scale value may be appropriate.)
But even apart from such an option, map developers are already able to minipulate attribute colors in any way desired.
To illustrate, here's a pair of lines from my own MWPRJ file:
<ShapefileCategoryClass Name="EDGEWATER" Expression="[COMMUNITY] = "EDGEWATER"" Value="EDGEWATER">
<ShapeDrawingOptionsClass FillColor="13952764" FillColor2="13952764" LineColor="4224439" />
It's a simple matter to scan the MWPRJ file, find lines with the desired attribute, then modify the colors on the following line according to any desired algorithm.
This is the strategy I employ to "proportionalize" the colors in my own project, which is designed to map statistical data from political elections. The data includes both raw counts and percentages, and both types
are better portrayed through proportional spacing.