are they all essentially the same or does each color mean something different. I have read that some of the covers, for example the Burgundy is softer than other colors, and that the Black is one of the hardest covers of the group and doesn't resurface very easily.

I think this is how they went in terms of oil to dry, but someone can jump in and correct me if I'm wrong:

Burgundy
Blue
Red
Black
Red Pearl/Blue Pearl
Pink

Cobalt Bomb is right that how this really translates on today's lane conditions is another question, but I can say from experience the Blue still works on THS for a down-and-in shot and the Pink is the best dry lane/spare ball I've ever thrown.  The Pink is also the hardest, and therefore hardest to resurface.

I can say the Burgundy is still a monster on today's conditions.  Had to have mine polished and it is still a strong ball.   It's the first ball out of my bag. 

If USPS ever finds it, there is a Red on its way.....though I think Sandy took it out to sea.    

From what I know, the previous posters were right on with their assessments as to the strength order of the different colors. On an interesting side note, about a month ago I was speaking with an older bowler who had first-hand contact with the folks who poured the old Faball Hammers. He claimed that the dull blue Hammer actually had a silica additive in the coverstock, so, in essence, it was something of a particle ball. Interesting concept. Whatever the case, all of those OG urethane Hammers were really, really nice balls in their day.

I almost won a blue pearl hammer in an eBay auction last year.  I won a nib black hammer auction.  Bummer. I wanted both. 

Yeah, the Blue always looked like dusty it was so dull, and the Burgundy used to give off a unique smell when you drilled it. I loved my Burgundy, and if I still had it today, could probably use it everywhere there was head oil.

If Hammer had any brains, they would rerelease the Pink Hammer.

Hammer would do good to bring back the Blade series core. Hammer weightblock with a pancake on top. Weightblock rolled well. I loved equipment from EBI that had that mod to it. The Vicious was good, Ebonite Pantera, Afterburner, etc etc etc.

I have to agree with Doom on that one. I LOVED the Blade series. The original Blade Solid and Blade Pearl were awesome pieces, and they looked good too! I owned 2-3 of each of those.