Hello all, I'm a newbie here but I do have some experience with display technology. One item that is well understood in my field has to do with the contrast ratio of text and it's readability. The luminance ratio of the text vs background is much more important than color contrast. So, for example, orange over grey may have seem to have a lot color contrast but the luminance contrast is bad. Why is that you ask? Well orange is made of "high luminance" colors green and red. Blue is a very low luminance color. Grey is a just a darker white with equal amounts of red, green and blue. But the luminance is mostly due to the red and green. Therefore orange on grey may be "iso-luninant" , and that makes reading difficult. Iso-chrominant is not as much of an issue. However there are bad choices here as well, for example , saturated blue on black (blue has low luminance). Unsaturated colors, by definition, contain more white (an added amount of red, green and blue together).
To make things readable, I recommend choosing a basic scheme first - e.g. darker (less luminant) text on lighter (more luminant) background. The extreme is, of course, black text on white. Then choose darker colors for text - such as a darker orange. And lighter (and generally less saturated) colors of background (light grey).
Don't feel bad that the color scheme needs improving. Google is still have issues getting theirs right.