//header
struct SysColors
{
   Color paper;
   Color ink;
   Color mark;
   Color highlight;
   ...
   void RefreshColors();

   ...

   static SysColors scs;

private:
   SysColors(){ RefreshColors(); }
};
Color& SColorPaper = SysColors::scs.paper;
Color& SColorMark  = SysColors::scs.mark;
//cpp
SysColors SysColors::scs;

Blend(SColorPaper, SColorMark, 220)