Well, by reading the manual i mean was u have to understand the basic meaning of those setting, i.e ISO is for what, Aperture is for what, bla bla.. but if u already know that, than that's good..
Then from that knowledge, try to think what setting u need to do to get the colours right.. But since u said that the problem is getting vivid colours, i guess it is a matter of:
1. try not to shoot subject while ur lens is facing the sun (make it on ur back)
2. reducing glare by install UV filter or lens hood, or a CPL
3. A little bit of post-editing to tweak the colours
And yes, natural light is 1000 times better than a DAMN BIG external flash unit with some white s**t sticking on it...