Applying a different color to something

[Valentina]

I would like to learn to paint objects without loosing texture and volumes. Is there any tutorial on this?
My immediate need is to apply bright solid colors to food (fish, cheese, steak particularly), sometimes I need to add stripes and dots (that follow the shape of the food).

A great example of what I would like to achieve:

http://www.floraborsi.com/191724/8428601/gallery/david-bowie

[Damien Symonds]

This is such a broad question.  It varies a lot depending on what you're manipulating.  So I'll need you to show me the photo you're working on.