colour interaction

I am getting more interested in colour interaction lately and I feel I have developed a slightly better understanding since I started.. which was basically sky=blue people = orange, sea= well...blue darker than sky.. as hopefully you can tell from this one. My simplistic colour theory goes something like this:
background colours: cool and warm greens for trees, cool blues and greys for sky, mid-ground reds, purples & warm blues for people. Foreground - pale yellows and oranges.