Apply a gradient to a border.
If you've got an otherwise simple design, and you want to use brand colours to highlight an element, you could put a border around it and apply a multi-colour gradient to the border. This is good for grabbing attention.
If you've got lots of other colour happening in the design, this can look over-the-top. If your element (The circle below, for example) has a fill, a colour gradient becomes much harder to do well.