Here I have used a flat one stroke brush. First I wet the brush with clean water. Then I load one side of the brush with indian yellow, then carefully dip the opposite side of the brush into a small pool of crimson lake.
With one quick circular swash of the brush, I have created a multicolor flower petal. The yellow and red blend together on the paper.
This is an excellent technique for quick, fresh multicolored flower petals. Works great for leaves too.