fix [#25283] Edge length display difficult to read

fix [#25283] Edge length display difficult to read
- made theme colors for mesh edge len & face angle/area display.
- use %g rather then %f for float display, trims unneeded zeros.
- store cached 2d and 3d text color as bytes rather then floats, compare when drawing to avoid setting the context.
- use unsigned char for more color functions, avoids casting to glColorubv().