Colors in mobile menu icon

In tablet or mobile mode, the menu changes to the usual “hamburger” icon. Where are the color settings for this? On my pages, by default it appears with white lines on a blue background, and after having been tapped it is white on a black background. I need to get rid of that blue color!

(Astra Pro is genuinely great, but with so many settings it is often difficult to figure out where specific settings are kept)