Question

Which background style adds a multicolored side background

Answer 1

$\huge\tt{★}\tt\red{A}\tt\pink{N}\tt\blue{S}\tt\green{W}\tt\purple{E}\tt\orange{R}\tt\orange{:-}$

Essentially, the background property can hold two contents one over the other: 2 gradients, 2 images or you can mix-and-match any of those. To use more than 2 colors (because why not), put the powerful rgba() to use and use 2 gradient parameters.