ATC = Artist Trading Cards. They measure 2.5 x 3.5 inches.
Our theme was quite broad!
1. Use your least favourite colour in your ATC.
2. Use your least favourite colour with your favourite colour.
3. Use your favourite colour and forget about your least favourite colour.
4. Choose your own theme and forget all about my suggestions.
I misremembered the instructions and worked for some time on some least favourite colours which of course did not look attractive because I expected them not to! So I made the following by using bits of abstract paintings that I liked and adding figures.