Does painting an interior wall with two coats of paint instead of only one change the color. For example, does it make the wall color darker, deeper, etc. If the wall color is brighter than you expected, will two coats of paint darken the color a little? Or are you just stuck picking another color?

If you don't like the color a second coat will not change it.

2 coats are good for a more even look or painting a lighter color over a darker color. It will give a better look and hide the color below better. But if you are painting onto a white wall 1 coat should be fine.

It will take 2 coats to get the true color of the paint, it will be a deeper tone on the second coat.