what causes variegation in plants
A common cause of variegation is the masking of green pigment by other pigments, such as anthocyanins. This often extends to the whole leaf, causing it to be reddish or purplish. On some plants however, consistent zonal markings occur; such as on some clovers, bromeliads, certain Pelargonium and Oxalis species.
Because the variegation is due to the presence of two kinds of plant tissue, propagating the plant must be by a vegetative method of propagation that preserves both types of tissue in relation to each other.