Older, white trailer is yellowing

I just finished bringing the yellow paint on my trailer back to life with a product from Turtle Wax called Color Back. I can't believe the difference it made. I thought I was facing a repaint but it looks like new. Easy to use, with great results. It's probably a liquid polishing compound. I have painted aluminum, like you. If the surface of your paint is still glossy, then it may just be an off-white color. If it looks dull or faded, then try using this on an out of the way spot and see how it goes. The white portions of my trailer were still fine, just the yellow had faded. Not sure why, other than white reflects more sunlight.