How should I attempt to remove???

We borrowed some snow gear from friends. DS1 was exploring and playing with his pale blue and white mittens on and they got dirty. I thought just dirty.

Dried them out and thought it might brush off. No.

Hand washed in warm water and wool mix. No good.

Machine washed on gentle with smidgen of liquid (as directed). No luck.

Stains/dirt/whatever it is remain.

Suggestions??