For curb appeal and aesthetics the mailbox should match your house.
However as long as you don't live in an HOA "Home Owners Association" neighborhood then your mailbox does not have to match your house.
I don't live in an HOA neighborhood and I have a curbside mailbox which is just a nice looking mailbox on a wood post.
I have some rocks around the mailbox and a little flower garden to make the curb appeal look great.
So you could put a little flower bed around your curbside mailbox to add some great looks to the mailbox and make it look great and add curb appeal.
But you don't have to do that.
If your mailbox is mounted on your wall then it does not have to match your house color etc either but having it the same color or at least the same color as part of your house makes the mailbox and house look great.
Also make sure to have house numbers for your address on your house and your mailbox if it's a curbside mailbox.