Warm soapy water and a brush, the same as G10. Micarta is waterproof for practical purposes and needs no conditioning. The difference is that it stains more readily than G10 and darkens with use, and a light sanding is the way to reset it if you want the original color back.
Soap, warm water, an old toothbrush for the texture. Micarta is cloth in phenolic resin, so water does not penetrate and nothing needs sealing afterwards.
Dry the knife properly, mainly so water does not sit in the pivot.
Lighter Micarta, especially natural and tan, picks up skin oils, ink and dye. Over years that produces the darkened patina many owners specifically want.
If you do not want it, fine sandpaper takes the surface back. Work evenly across the whole scale rather than spot-sanding, or you will end up with a patch.
Sanding also reopens the surface texture, which is why worn Micarta grips better when damp than polished Micarta does. Restoring the color and improving the grip are the same operation.