NO! You can't wear white, ivory, champagne, beige, etc. Any solid light color dress will make it look like you're stealing focus from the bride. No matter what color the bride is wearing, you cannot wear white, ivory, cream etc.
No. No white, no ivory, no eggshell, no cream. That is the one rule about wedding guest attire - you have a whole rainbow of colors to choose from, so be classy and wear the cream dress to a non-wedding occasion.