I worked for awhile just to get a good looking sky in Pico-8... Four colors is a fun and challenging restraint !

(saving the green for cacti) Western theme! 

Show me your screen shots!

Here's what I've got.
Not much, but I'm enjoying it so far.

You could use dithering to make the gradients a little bit easier?

Two screenshots, works in progress.   I'm feeling that  flat color is working better for me then dithering.  Anyone else feel dithering starts to look busy on small screens?  I'm emulating the look of the gameboy resolution.

Yeah, I agree. Dithering is okay when you've got room to spare and actual colors to blend, but here you've only got like 2 colors to shade with.
I think it can still look okay in a low resolution, but the colors are too different to work with dithering.

You just have to be creative. think in mono and then add some color. Have a look at these:

All cya 4 color....