Use a Color palette

Use a Color Palette

Low Poly renders typically have less detail and fewer colors than photorealistic renders.
Using color palettes is perhaps the fastest way to explore different color themes to find which one works best for you.

Good Tools for Color pallets are Adobe Color, Which also integrates in every Adobe Software or Coolors

STICK TO ONE STYLe

There are a lot of different styles for low poly renderings. Most of the time, it makes sense to stick to one style, which also accounts for polygon distribution patterns.

Use ACES for colorfull low poly renderings

If I see a stylized render of any kind online, I can often recognize, that it is made in Blender. They look less colorful and overall a bit more pale.

The reason for that is the filmic color space, which is the standard color space in Blender today. But compared to the RGB Color space you lose a lot of color, ACES combines the best of both worlds and will probably be the standard color space in the future of Blender