How to Change this Gradient

I’m trying to change the gradient color that runs across the top of the page. The problem I’m having is that I can’t identify what the section is called in the code.

The webpage is: https://hardmonkey.com/

The part I’m trying to change is the gray to white gradient across the top, the part directly behind the HardMonkey logo.

I’ve looked at all the css colors in the style sheet, checked all the images in the theme folder, and I can’t find anything that matches it.

Could somebody tell me what part of the code it is in the style sheet?