what colour counteracts brown undereye circles?

usually brown has some purples in it, so yellow covers that up

Yellow usually does the trick but it also depends on the EXACT color of your circles. There is a product sold by Color Me Beautiful, called a concealer wheel. It has a turquoise for red toned circles, a pinkish color to counteract greenish under eye circles and the yellow that counteracts brownish purple. I have found that there is nothing that this wheel cant make disappear.

http://www.colormebeautiful.com/makeup/concealers/...