Bought 2 pans and mistakenly threw them in the dishwasher – discoloured now, but is it still safe to use?

This is the aluminum hardening on the surface, the colour can effectively alter or change depending on the hardness of the water, and other factors. This is a natural process known as seasoning. This discolouration can be removed with vinegar or lemon juice, the discolouration does not impact the performance of the pans.