DIAGNOSIS The projector's lamp is nearing end-of-life or has degraded significantly. This is the #1 cause of faded, dim colors on 3LCD projectors. The color brightness (measured in lumens) drops as the lamp ages.
FIX Check the lamp hours. Go to Menu > Settings > Reset > Lamp Hours. If it's over 2,000 hours (and especially near 3,500), the lamp is the culprit. Order a genuine Epson ELPLP89 replacement lamp. Follow the precise procedure in to swap it—it's a straightforward user-replaceable part.
IF THAT DIDN'T WORK The Color Mode might have been accidentally changed. Press the 'Mode' button on the remote to cycle through Dynamic, Living Room, Cinema, etc. Also, go to Menu > Image > Color Mode and reset to a default like 'Dynamic' to see if that restores saturation.
HEADS UP Never use non-genuine or 'compatible' lamps. They often have incorrect UV filters and can cause color imbalance, overheat, or even damage the optical engine. The cost savings aren't worth the risk.