I have since found out that this was not what the prompt actually meant, but I did it anyway! :)
I'm not crazy on how it turned out. It's kinda messy, and the colours make me think of mud! (I suppose the polish is called Mudslide Tote for a reason!!). It's probably my least favourite mani of this challenge so far.
I used Maybelline Mudslide Tote and Revlon Trade Winds to create this reverse gradient.
Have a look at the other, much better entries below!