To change colour....
1. Select the Lasso tool, second tool first column in the toolbox pallette.
2. Select the shape you want to change the colour of.
3. On the menu bar choose: Select > Feather... give it 1 or 2px to give the selection a soft edge.
4. Once your happy with the selection choose: Image > Adjust > Hue/Saturation from the menu bar.
5. Grab the Hue slider and move left and right to change colour
There's probably other ways but that's how I do it
This is using PS9 but 7 isn't that different .