I noticed the matching colour, here in the picture below.
It is always a good idea to look at colour while you are shooting. And you can learn to notice. Start like this: If anything strikes you: shoot!
Harmonious colours, is how we describe colours that are close together (as opposed to contrasting colours, which are opposite, like red-green, or blue-yellow). The above shows harmonious colours. These strikes us as gentle, soft, understated, even.
Taken at “Tribe” on 24 October 2009.