Do my cactuss look like they are dead they havent been watered in a while

They don't look dead to me.

What are you seeing that makes you think they are dead? Could you retake your photos? They are back lighted making it very difficult to see them.

From what I can see, they look fine. They don't need much water, but don't forget to water occasionally.

As long as they're not brown and shriveled, I'd say they look pretty happy. As Daisy said, it's a little difficult to see the color in your pictures. Cactus prefer to be dry rather than too wet, as I'm sure you know. Overwatering them kills more cactus than months of no water.

Looks like they might be growing in a too moisture-retentive potting mix, though. See if you can get some that says "Cactus and Succulents" and then you could re-pot them in a large shallow pot together for a cactus garden. It's more difficult to overwater if you have them growing in a coarse, gritty mix. It doesn't stay wet as long.

Thank you very much for your replies you have all helped me a lot.
What made me think they were dead was one had purple on it and the other has yellow spines and is shriveled .Both things that weren't there when i bought them. Does anyone know why this has happened ?

Maybe a maturing or ripening process. These are living things, and although they grow slowly, they do change as they grow. Increasing temperature and light stimulate new growth in spring, and less light/heat can make them ripen their blooms/fruit and slow down.

I'm not seeing the purple color you mention. Can you get a better picture? But really, as long as the body of the plant is green and firm, they are doing fine.

I hate to be the one that bursts anyones bubbles but I don't think they are doing very well. The purplish one may be rotten, the larger one should not have brown shrivelly sections. The little one looks good right now.

Soil formulated for cactus and succulents is a must for growing cactus indoors. Putting a bunch of cactus in one bowl will just amplify the problem if overwatering is the problem as there is a lot more soil than is needed. Drying out thoroughly between waterings is imporatant.

Still waiting for better photos...