They look nice.The second must be mammillaria bocasana cv fred.

On a second thought, in the first picture the plant has a brown colour and at the bottom is green.Why is that?

I’m guessing the first one’s color is due to sun. Not sure exactly. Here is a shot where you can see the green underneath

Oh, I didn't realize it was so small! It does look healthy, great find. Could it be a rebutia cristata?