When setting colors on the Image History Graph, the numerical values do not change colors as shown in the attached image. This may be as per your design and is OK.
Also, it would be helpful to be able to set the Background color as you can in the PHD2 graph. It would also be good to save the background colors in both PHD2 and IH graphs so that the color scheme is preserved for the next time SGP is launched.
Link to Logs
OS: Windows 10 Pro