Changing color of Web Chat for Service Prelaunch for collapse icon and title(?) text

Summary:

I'm trying to change the color of the Web Chat for Service Prelaunch for collapse icon and title(?) text (not the header).

Content:

In Web Chat I'm trying to change the color of the word Chat and of the Collapse icon to white.

I believe the collapse icon is in
Functionality Configuration --> Icons --> Collapse
but when I try to change the color there, it does not work, even though it works ok in an SVG tester (https://www.w3schools.com/graphics/tryit.asp?filename=trysvg_myfirst)

Here is one of my attempts, in this case trying to set it to pink to conform it's having an effect.