When you do studies from photos, I highly recommend you pick/mix your own colours instead of sampling from the photo. This will teach you to really think about how and why the colours look the way they do.
When it comes to picking palettes, brush up on colour theory (this tutorial covers a lot of ground, though not in a very practical manner
), and do some palette studies, where you just paint random things (maybe even blobs), but try to do so using colour in a pleasing way. One thing you can do to quickly experiment with colour is to make a bunch of shapes on separate layers that form an interesting composition in grayscale, then fill those layers with different colours and try to discover the pleasing combinations. Use what you learn from the tutorial to guide you, but don't be afraid to do weird stuff. When you find a combination that works, try to figure out why, using your colour theory knowledge. When you find one that doesn't work, try to figure out why that is so, and perhaps think of ways to adjust it to make it work.
When it comes to choosing colours in a realistic fashion, these two tutorials helped me a lot:http://androidarts.com/art_tut.htmhttp://www.itchy-animation.co.uk/light.htm
It's important to realize that things aren't always the colour we think they are, and to use this in our work. Here are two photo examples:http://behindinfinity.deviantart.com/ar ... e-80327392http://fhrankee.deviantart.com/art/Deli ... -149527432
If you actually sample the skin colours, you'll see that one's skin tone is an unnaturally bright orange, while the other is a very desaturated blue. They don't seem outlandish to us in context though, because the colours of everything else are also shifted accordingly. So, the relative
colour of the skin remains "skin-like." In your studies, the statues have a yellow hue probably because of the lighting used. Other objects placed next to them would probably also be more yellow than normal. Ooor, maybe the material itself is more cream-coloured than you realize, and you just expect grey because it's what you're used to. It's important to learn to really see things and not let your brain fill them in for you.
Edit: Also, when I said "realistic fashion," I didn't mean "the colours that are really there" necessarily xP I sometimes use pretty unrealistic/implausible palettes in my work, but I keep the colours balanced so that things don't look weird in context. For example, if the environment around the girl in the second photo was warm rather than cool, then her blue skin would look weird, as if it really was blue.