I'd say unless the ad says you may be getting a different color bike than was pictured, you have grounds to dispute it with ebay and your debit card company for a full refund. Make sure the bike company has to pay the shipping. Call the company you ordered the bike from first and let them know that this is your intent if they don't do a partial refund. You'll have to make sure you're assertive when talking to them, though, or they're going to just treat you like a push-over. I'd have real issue with them sending a completely different colored bike than pictured. As for the assembly, I don't know if I agree with you or not because I don't know if there was any implication one way or the other in the ebay ad. In general, though, you did know about the overpriced shipping(That's Highly overpriced, btw), and if they didn't say anything at all about assembly, I'd say expect to be putting it together yourself if you order off of ebay. I'd still demand they cover All costs for return of the bike and you to be shipped the correct color, or they give a partial refund for blatant misrepresentation. There's no reason for them to be doing that other than half-assed lack of regard for the customer. And they only do it because people let them get away with it. Don't let them.
It does say it's unopened in original packaging. Not much room for complaint on lack of assembly there. It does also clearly say that the color is blue, though. I'd let them know they're going to need to pay shipping for the bike you got to be sent back and for them to send you the correct bike. Or they can just give you a partial refund of whatever you feel is appropriate depending on how much you have issue with the colors they sent you. I think it's crap if they have issue with sending you the correct colored bike, though, and I wouldn't put up with that. They need to take care of their mistake.