Orange is probably the toughest color group to achieve a good contrast ratio with. Oranges do not go well with many colors contrast-wise because they are usually the middle-of-the-road in terms of lightness. It's easy to turn the orange into a red, brown or yellow trying to adjust the contrast ratio to pass the WCAG.
But there is a (somewhat limited) trick. If you want a more vivid dark orange you will need to make it redder, and if you want a more vivid light orange you will need to make it more yellow. And that's pretty much all you can get away with if you don't want a pale pastel orange. (It also helps that many oranges are good against black, but having a good contrast with white would be much tougher without resorting to color psychology.)
Isaac Newton added orange to his definition of the rainbow and it stayed. Many objects in nature are orange and unlike indigo, it is distinct enough to be its own color. (Did you know that orange isn't even in the Munsell color model? It's considered a Yellow Red.)
General Rules
- The green channel will dictate how light the orange is. Lighter oranges will be more yellowish and darker oranges will be more reddish. Be careful with lighter or darker oranges as they can potentially get too yellow/pink for lighter oranges, or red/brown for darker oranges.
- It's okay to not have the blue channel on if your red channel is less than 100%/255.