Pickr – “Flat, simple, responsive and hackable Color-Picker library.” (more info.)
[lenards]
Category: color
‘modern’ color accessibility tool
Color.review — “colors that look and work great for everyone”
yet another cool image tool
SVG Gradient Map Filter
(other tools by the same developer)
‘selective contrast’ for terminal (or editor)
Solarized — “precision colors for machines and people”