Nice stylisation (sp?) going on. Going to look cool once slapped together with those fun characters moving about that world. Keep experimenting! Coloring on the 1951's-pic shows progress. Looking good. I'm not so sure about that on the purple one, but hey it's a sketch. The character in red has the best feel to it.
On the coloring subject: you might wanna take a look at the Practical light and color dvd from g.n.o.m.o.n. That's just a treasure trove of information. It helps to form your own point of view as it's suggesting to look very closely to the things around you. How light affects the color and so on. Might be stating the obvious, but the information is so true and you keep getting back at it every once in a while.
Jan van der Zee
edit: moderator: can't I say G-n-o-m-o-n ?