Complementary colours are opposites on the colour wheel. Put them together and they sing!
Blue/Orange. This is my favourite and the one I use the most in my paintings.
Red/Green. This combination is so ingrained in me as Christmas that I find it hard to think of the saturated combo as anything else. To avoid this I use two very different shades of the colour such as in these Croton leaves in darkest green and brilliant red.Dark red and bright green.
Christmas on a Belgian beach.
Purple/Yellow. This combination is particularly popular with flowers, especially spring ones, and always reminds me of Easter.
At full saturation they positively sizzle, spitting out equal parts of colour so fast one can barely look at them. This shimmery effect resulted in the psychedelic posters of the 60s and Op Art, but that’s another topic.