I've started on something today which I should have done much earlier - a color chart. I chose Azo red for the first chart. In the first column I've only mixed Azo red gradually with white, the second column with blue and white, the third color with yellow and white etc. This way, if I for example have a photo and want to use a special color in that photo in my painting, I can just compare it to my color chart. That way Illl know exactly how to mix that specific color.
To complete the chart I have to mix Azo red with all the primary colors plus orange, green and violet. Maybe even earth tones and other colors which I use often. Then I need to make one separate chart for each of the colors mentioned above. Lots of work, but I'll do it peu en peu. I think it will be worth it.