When I bought my bike from craigslist, it had a blue frame and mostly silver components (except the crankset and cogs, which were black - so stem, seatpost, bars, fenders, rack, wheels...). Through some upgrades (new seatpost/saddle, brake levers/hoods, bars, stem, tape, rack), the accessories are pretty much now all black except the rims and fenders. I have a new front rack coming tomorrow that's also black and I'm starting to think that silver fenders with everything else black looks a bit dumb and have been considering switching over to some black fenders. I'd probably want to do that before I put my front rack on, so I only have to put it on once. The thing is, the fenders I have now are aluminum and in pretty decent shape; they just don't match the color scheme. The fenders I've been looking at are the planet bike hardcore plastic fenders with mudflaps.
So I'm debating whether it's worth the $30 to make the change for purely cosmetic reasons and if switching to plastic fenders from the metal ones I have on there is going to be a serious downgrade in quality/durability. I'm not at all concerned about weight as I just put a handlebar extension on and clamped on my Wald collapsible baskets to the rear rack this last weekend and the front rack is going to weigh a couple pounds (Jandd Extreme rack).
And yes, it's probably stupid to worry about the looks of a purely utilitarian bike, but it's the only one I have, so it's my do everything ride (recreation, exercise, occasional commute - I'm car free and mainly take public transit but want to get more into bicycling for most things) and I'd like it to look as nice as possible. I've bought new derailleur cable/housing I'm going to put on at some point because the current derailleur housing is a dirty gray and looks odd with everything else (including the brake cable housing) black, but I haven't gotten around to making that particular switch yet as the shifting is quite nice and I don't want to screw it up (my wrenching skills aren't all that yet).