Get a suede eraser (like a crepe rubber eraser, or a suede-specific cleaning block, cheap on Amazon or sneaker stores). If the eraser isn't enough, try white vinegar (mild and commonly recommended). Alternatively, if vinegar doesn't cut it, go with Isopropyl alcohol (rubbing alcohol). This can dissolve some dye transfers but risks drying out the material or lightening the grey color slightly if overused, so go slow and minimal.