no, the blue mega drive was actually realeased for a limited time in 1993 for sega, and they are (i think) rare today. not really rare but like gold N64 rare.
You might be thinking of the blue Game Gear. I don't recall an official blue Mega Drive, but maybe you could teach me something new.
Mine's just a paint job.
I had a broken Mega Drive 2, so I thought I'd have a go at painting the shell. I chose blue partly on an impulse while I was in the hardware store buying the new shelves. I was thinking maybe blue or red, then I saw a small spray can of a neutral blue enamel paint. That was about £2.50 for 100ml.
I gently scuffed up the surface with some fine wet and dry paper, then washed it with white spirits. I used sticky backed plastic to mask up the black ring and SEGA logo, and also the serial number sticker underneath. Then I sprayed three coats of blue across about five hours. I should probably have waited longer but it said it was quick drying. I looked at it this morning and I decided I didn't like the glossy appearance it had. I needed some lacquer to protect it, anyway. I went to the hardware shop and the only lacquer they had were big £8 cans, which is far too much for this. I ended up going to a model shop and got a 150ml can of matt lacquer for the same price as the paint.
I think it turned out really well. I like the smooth look to it. It's not perfect but most of the small blobs are on the bottom, where they don't matter.
The picture of the consoles is a bit out of date. I've got a 2600, a Dreamcast, a surround sound system, and a PC monitor on the desk now. But it's too messy to get a good picture of it all. I really need to work on tidying my desk some time.