After reading your response, I went back to my site and tried again.
I can set the Background color for the icons in the About page, but whatever values I enter into the Icon Color itself, none of it matters, the icons will stay blue. I tried it with each of the 4 icons on that page, and I get the same result for all of them.
I then investigated further, and finally found the reason why: there is a "Style" box in the settings of the Classic Icon element, way at the bottom of the left panel of Cornerstone, and I found out there's a whole line of styling in that box:
"display: inline-block; width: 3em; height: 3em; border: 4px solid; font-size: 2.5em; line-height: 2.875em; text-align: center; color: #02aed6; border-radius: 100em;"
So then I just went in and changed the color value of the style, and got the icons to finally(!) turn into the color I wanted.
Thanks for your response, it made me try again, and allowed me to make that discovery, so all is well - for now.
Have a great day/evening, wherever you are!