Why are there solid-colored leaves on my variegated hosta?
Variegated hostas are hosta mutations of cells in one or more layers of the leaf. These variations are found within the plant cells, which are called "plastids." Plastids contain different colored pigments, and largely determine the color of leaves. Plastids can be orange, red, yellow, brown, white-ish, and colorless. When a mutation occurs, the normal ratio of plastids is rearranged. Some colors become more abundant, and the leaf takes on a variegated look.
However, not all hosta mutations are stable. As such, this means that hosta mutations can revert back to their original pre-mutated state, or they can continue mutating.