I'm with mammo. When I got my crowns my dentist matched the crown to the surrounding teeth so that they wouldn't stand out. I just got an immediate denture and he did the same thing.
There's no need to replace all 4, and if he's a good dentist he can put on a crown that won't appear newer than the others. Dentists are always upselling. It's an expensive process, you can always have the one done and if you don't like the appearance, do the others. Don't tell your dentist this, just tell him due to finacial situation you would like for him to do the one and make it not look newer than the others. If he knows you will have the others done if the one doesn't look good, he has no incentive to do a good job on the one.