The front of my washing machine has gone yellow.

[Fluffycloudland77]

Just on the control panel and the rim of the door.

Does anyone know how to get it back to white? It's been in a garage for 3 years.

Is this a plastic part?

it's probably absorbed something that has stained it. IME it is unlikely to go white again. Some pollutants dissolve into ther pastic so you can't just scrub the surface. You can have a try with a kitchen spray, or expose to sunlight, but I don't think it will work.

It's a long shot but maybe try whitening toothpaste and a good scrub!