I see nawo continues his quest to become Onikobe Rin.

Here's a Photoshop tip to achieve colors like this:
1) Paint your picture with the usual light palette you usually see in japanese pop-art.
2) Duplicate the color layers and join all the duplicates in a layer with all the color.
3) Place this layer over the original color.
4) Go to Layer Blending options, choose Color Burn.

There, your colors are now darker/warmer.