Generic Color Structs

[ds5678]

Many of the current color structs could be replaced by a handful of generic versions:

• ColorR<T>
• ColorRG<T>
• ColorRGB<T>
• ColorRGBA<T>
• ColorA<T>

These would be enabled by a pair of helper methods:

static T GetMinimumChannelValue<T>();
static T GetMaximumChannelValue<T>();

The implementation of these would take advantage of JIT optimized code generation to avoid any performance issues.