Not sure what you mean? All toys (not just white) will discolour as it ages. Some faster than others (depending on its environment). My Dekabike came white as snow. Even though it was in storage for a while I recently dug it up and a lot of parts had become yellow :(.

The Dekaranger stuff only appears to be more prone to yellowing. Seeing as most of the figures are white people tend to notice it more. Though they arent more or less suceptible than other newer DX's.