What can I do to cover the blue tile in my bathroom besides replacing?

One do-it-yourself option is to paint the tile ­using a special primer, such as XIM 400, that is formulated to bond with ceramic tile. XIM ­Products's technical rep Dan Ryan says you first have to roughen up the tile surface with 220-grit carbide sandpaper or XIM's muriatic-acid-based deglosser. Then, to get the smoothest results, he recommends spraying on the primer—and the paint—rather than brushing it on. Ryan says oil-based paint works fine on tile that won't get soaking wet, but in tub or shower areas, a two-part epoxy-based paint is required. Its colors are limited to pastels.

Hi Moxie, My whole bathroom was 50's blue tile. When I tried to take it out, the wall wanted to come with it, so I just used peel n stick glass tiles to cover it all except the boarder around the top and bottom. It's been 3 years and I've had not trouble with it, and this bathroom as no vent.

Hope this helps!

It can be painted

Get a good primer, then paint them. I would also use a sealant to "waterproof" them. Good luck.

You can also cover them with beautiful tile stickers, https://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=tile+stickers

You can paint it, here's a good DIY to give you some ideas. https://www.hometalk.com/diy/paint/how-to-paint-a-floor-with-a-tile-stencil-31754162

Smart!! Very nice looking too.