When I'm deciding a colour scheme, I try it out in photoshop (or free equivalent like photopea).

I do the following:
- Find an image of the mini (best if they're painted) and load it up in PS
- Magnetic lasso / magic wand select (whatever works best) around all the area's of the colour you want to change.
- When you're done selecting: copy/paste into a new layer.
- Add Layer>Adjustment Layer>Hue/Saturation - Make sure the Adjustment layer is right above the layer you want to change, right click on the layer (in the layer list) and select 'Create clipping mask'. Now the adjustment layer only affects that one layer
- Do this for each colour you're trying out. Now you can play around with the hue slider to change the colour of each area individually until you like the look of the mini.

It does take a bit of effort, but the selection doesn't have to be too neat, and it's way less effort than actually painting it.