I had an epiphany recently while sourcing fabrics with a client. She turned to me in utter frustration and said, "What on earth are you talking about, 'This blue is more red and this blue is more green?' All I see is blue." I realized then that it's not choosing colour that's difficult; after all, we know instinctively what we like and what we don't. The confusion lies in recognizing the subtle presence of undertone, the colour underlying the colour. Wait a minute you say, how can colour have another colour? Since most colours are mixtures (orange = red yellow), a certain amount of "ghosting" occurs, allowing undertone to dramatically alter the final colour. Here's how to make sure undertone doesn't undermine your decorating.

Dos and don'ts
DO analyze colour in elements from your decor, a red orange terra-cotta pot, for example. Find the undertone in the pot (remember, orange is red and yellow). Once you identify that colour, you may use other yellow tones, since they'll blend harmoniously with the terra-cotta.

DO consider undertones when choosing wall colour. If you love green but want a subtle effect, pick a white or grey with a green undertone.

DO learn to identify colour tone -- the warmth or coolness. A warm blue will likely contain some red, which makes it more plum, while a cool blue will contain some green, which makes it more teal or aqua than apple.

DO be ready to make mistakes. To find the right colour, complete with the right undertone, you may have to invest in several paint samples.

DON'T emphasize an unwanted undertone by pairing it with its complement. If the maple cabinets in the kitchen seem too pink, green (the complement of red) on the walls will intensify the problem.

DON'T forget that neutrals have undertones. Many people mistake grey for green if there's a green undertone, or plum if the undertone is purple. To determine the undertone in a grey paint you are considering, compare it to a "true" grey paint chip, which has no colour (only black and white), available at any paint store.