Use id16 instead of id256 for color id

[kazarmy]

Probably will use different approach to map to 256-color table.

[codecov-io]

Codecov Report

Merging #14316 into master will increase coverage by <.01%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master   #14316      +/-   ##
==========================================
+ Coverage   37.85%   37.85%   +<.01%     
==========================================
  Files         950      950              
  Lines      305758   305758              
==========================================
+ Hits       115731   115733       +2     
+ Misses     190027   190025       -2

Impacted Files	Coverage Δ
libr/cons/pal.c	63.58% <66.66%> (ø)	⬆️
libr/cons/rgb.c	49.48% <83.33%> (ø)	⬆️
libr/core/project.c	57.81% <0%> (+0.33%)	⬆️

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