I would suggest staying away from ms paint default colors. If you are starting out, it may be a good idea to try to use an existing palette. You could also try to look through the custom colors and mess with the hue, lum and saturation until there is something you like, or at the very least edit the defaults.
There seems to be no lightsource in the image, and there are a few jagged areas in it.
It's a good start though
also, I started on a toadsworth sheet in sma4/smb3gba style and I also made a few changes to the spearman and wario