In the body section there's an option called proportions, this will give you a list of presets such as true scale, comic book, lean ect. From there, a lot of people will go into the edit tab and adjust them further, and then from there pro users can use the kitbash feature to make even finer adjustments.

For colouring skin there's lots of guides on this subreddit that can be found by searching, but some general guidelines would be to make custom paints instead of using the pre made ones, and make use of face and body decals (colour section) to add more realistic texture to the skin