I've had a black-painted 7x7cm canvas hanging around since Hallowe'en last year. It occurred to me today to use it for flowers. (Because they are there.)
First, I blocked out the tulip area in white:
Then I added the colours. Three of them. Magenta, phthalo blue and lemon yellow are all fairly transparent colours, which is why I knew that the white was required. I tried to just use glazes (water-based, in this case) - sometimes this will keep the colours brighter and warmer - but there were plenty of places where the white got added back in, by itself or as part of a mixture.
Acrylic on canvas, 7x7cm