How to configure the appearance of eglot inlay hints?

[Raincole Lai]

I'm not sure why there seem to be two "styles" of eglot inlay hints by
default.

For example: https://i.imgur.com/d0BqGN3.png (Sorry for external links.
It's impossible to explain my question without an image.)

In this piece of Rust, the inlay hint of "input" looks like "inputString:
", while the inlay hint of "index_digits" looks like "index_digits: usize".

In my opinion, the former is very hard to read. Even worse when the
variable is unused: https://i.imgur.com/CAmYZoM.png

How could I make it look like "input: String", just like how eglot display
the hint for index_digits? Or could I customize the appearance so the inlay
hints have a different background color?