I think the pattern is red-blue-yellow. They are all primary colours. You can mix primary colours in different quantities to make other colours. We see a yellow buttercup because the petals absorb green and blue light but reflect yellow light. The petals are flat and strong and glossy. They are so good at reflecting yellow light that when I hold the buttercup under my chin it glows yellow. It’s not really anything to do with butter, although I do like that too.
