Green skin with orange plates may look good, it would be good to try a scheme out on one model and see how it looks.
I use knarloc green whenever I need a nice green tone on anything, the other greens are alright for brighter colors, but knarloc green is my favorite. A quick tutorial would be to paint the entire model green and paint the plates you want in orange as orange. You will then want to use a good wash like devlin mud to bring out the scales and create some nice shading effects. So:
1. Basecoat with green, if using a foundation like knarloc you only need one coat really.
2. Paint the areas you want to be orange.
3. Finish it off with applying devlin mud wash to the entire model. Do not over do a wash, try to keep it light, then add on to any parts you would like to add to.
4. If you like it the way it is you are done, other than that I would suggest touching up on the model with some highlights and metallics. But all of that is optional, you can have a good looking model without highlighting.
*Since you are a beginner, it would be good to note that whenever using paints it would be wise to slightly water them down to make the coats thinner. This can easily be done by dipping the paint brush in the water with paint already on it and spreading it around on a small pallet. The even easier way to ensure a thin coat is after applying a coat to run the brush over areas that look too thick to even them out.
