How are colours added to felt?

Because of the type of fiber wool is color must be added with an acid based dye, which are actually harmless, Kool Aide is actually a kind of acid dye. These dyes are added to water and heated to make the dying process work. Acrylic or synthetic felts are made from colored plastic pellets which are melted and poured in strands to make felt. Andie- www.americanfeltandcraft.com