Thanks a lot, Matt. You made my day. ;-)

Given then that purple is blue and orange is red, how does a tartan designer unambiguously specify the required colors?

By way of example, suppose a designer wants a tartan to contain repeated bands of the colors (you'll never guess) blue, orange, purple, and red. How are the four colors specified so that the orange bands looks like the fruit on the orange tree and not a tomato, and the blue bands look like the deep ocean on a sunny day and not my face now, as I'm holding my breath?