When concrete is thoroughly dry, paint base coat onto mushroom top and stem. When the base coat is dry, use a brush or sponge to add a shadow of a darker color around the mushroom top and streak it onto the stem. Dab on a (third) lighter color accent until you like the way it looks.
I used Americana Acrylic paint
BASE COAT: Cocoa
SHADOW: Burnt Sienna
THIRD COLOR: Celery Green
Don't stress over the paint job...you're just looking to add a little dimension.