I'm pretty sure the top panel is secured by the chrome trim strips on both sides of the door. You only have to remove one of them to insert the colored or stainless steel panel.
Same goes for the bottom panel, but installing that whole panel assembly onto the machine can be really frustrating. You have to angle it out at the bottom and inward at the top, lift it up and over the tabs that hold the top edge in place, then attach the bottom L-brackets to the frame with screws. It could easily take you several tries, as it's mostly done by feel. Always pull outward at the top to make sure it's securely hooked. It will pull right off if it's not. Don't bother doing anything with the bottom until the top is properly in place.
My experience has more than once been that the top refuses to attach, but after a bunch of attempts it finally does, but I never have any idea about what I did differently.