If we mixed green and blue paints we would get a greenish-blue paint. Mixing in brown would give mud. Eye colors of children came out as pure green, blue, or brown, not as a mixture of the colors of their parents' eyes.
Children can have different eye colors than either of their parents.
This is strange, if colors can't mix. It would make sense if colors mixed and blue and green eyed parents had greenish-blue eyed children. Brown tends to swamp out green, green tends to swamp out blue. Genes are structures that are carried on larger structures called chromosomes. The genes for each characteristic come in pairs, and the two genes together produce a given characteristic.