I used colour in my images many years ago to represent digits. What has changed over time is my palette for representing digits. The more colours I put on the palette, the more two colours or shades will look similar - and that is undesirable. There are three shades of brown in the palette picture below - and they are quite close to each other in tint!
By having this idea that a colour can indicate a digit (or represent a letter of the alphabet), it opens up the possibility of memorising information by remembering the colours of a picture.
I intend to use this feature in many of the images which I home-make. The colour of someone's hat or clothing top or trousers or hair can all mean something: digits or perhaps letters of the alphabet.
I would like to have a suite of games where the characters are introduced and learned by students - and then, later, memory games can be introduced to the student based on the colours which comprise them and any icons on their clothing.
The characters in the earlier lesson for representing digits 0 to 9 have had their colours chosen based on the palette.
I also like the idea that a filler pattern could make further use of numbers 1 to 25. Eg. A dots fill pattern could mean that a colour's number should have 25 added to it; diagonal fill can mean +25; and a grid pattern can mean +75
I think it is a reasonable idea if the image is close up; but, from a distance, a patterned colour can appear to be a mixture of its original colour and pattern colour - causing a different colour visually.
Now that I have a main system where a colour can mean a number, I can have images which mean months of the year; and colour those images in a colour that means a number from 1 to 12: for the 12 months of the year:
1. Orange tambourine
2. Yellow skin colour feverish person
3. Green marching traveller
4. Dark pink ape
5. Navy blue envelope: mail
6. Brown jug
7. Pink jewel necklace
8. Light grey organ musical instrument
9. Red magnet
10. White octopus
11. Light brown length of new ribbon
12. Blue-purple paper chain decoration.