Colour

Greetings,
I am interested in finding evidences about the role of colour in some
writing systems. I mean scripts that use colour as a meaningful
element or distinctive feature.
In the first models of auxiliary vocalization for the Arabic writing
(now made through little traits below or above consonants) distinct
coloured dots were utilized to represent different vowels.
Colour has been noticed as a significative element in Egyptian
hieroglyphic writing, even though i have found very little
documentation about this in classical egyptologist works.
Thank you in advance for your help.

Miguel Peyro