I don't have a lot of experience with editing the code, so I'm hoping someone can help me. My theme is Brooklyn and on my checkout page, I would like the accent colour for the "keep me up to date..." checkbox (the background of the checkbox) without changing the accent colour to everything else. Right now, you can't see when it is checked off since the checkmark itself is white and my accent colour is a very light blue.
The accent colour applies to the links at the top and bottom of the checkout, so I don't want to change them.
Alternatively, I would be happy to keep the accent colour (the background) light blue and change the colour of the checkmark itself to dark blue.
Any idea how I can do this?
The only color controls you have over the checkout will be via the Theme Editor (that you are showing in the images).
There's no option for controlling the color of every element (or an option for that specific checkbox) so you will have to find a compromise in colors that's appealing.