NOVELTY - Treating mushroom compost (waste mushroom compost), comprises either: (a) providing the compost comprising water to a first separator (a screen), (b) separating in the first separator the compost, (c) partially removing water to obtain partially dried material, (d) coloring the partially dried material with a colorant material to obtain a colored material, and (e) further removing water from the colored material to obtain treated compost; or partially removing water from the compost to be treated to obtain partially dried material, and steps (a), (b), (d) and (e) as above per se.    USE - The method is useful for treating mushroom compost, preferably waste mushroom compost, which is used as: an organic material; at least one of a mulch, a fertilizer, and cover of soil (all claimed); and protective decorative mulch.    ADVANTAGE - The method: provides the mushroom compost, which can be re-used, thus reducing negative environmental effects; is cost effective; improves stability of compost by reducing water; and improves the structure of the soil, thus providing available nutrients to soil.    DETAILED DESCRIPTION - Treating mushroom compost (waste mushroom compost), comprises either: (a) providing the compost comprising water to a first separator (a screen), (b) separating in the first separator the compost into a first fraction comprising smaller compost particles, and a second fraction comprising larger compost particles, (c) partially removing water from the larger compost particles, to obtain partially dried material, (d) coloring the partially dried material with a colorant material to obtain a colored material, and (e) further removing water from the colored material to obtain treated compost; or partially removing water from the compost to be treated to obtain partially dried material, and steps (a), (b), (d) and (e) as above per se. An INDEPENDENT CLAIM is also included for an organic material, comprising mushroom compost (more than 80 wt.%, preferably more than 98 wt.%), and colorant material (0.1-2 wt.%, preferably 0.5-1 wt%) chemically and/or physically bound to the mushroom compost.