The ColorAdd® system was developed by designer Miguel Neiva to allow those who suffer from different types of colorblindness to easily identify colors, and allowing them to interact with certainty in situations where color plays a key role like in navigation, reference and organization.

via Color + Design Blog / Color Identifying System For The Color Blind by COLOURlovers.

It’s a system of symbols that can be mixed to indicate different colors on maps and things.