I'm using the Corporate Clean theme as the basis for my site. I've customized some theme colors to my liking. I have installed the Mass Contacts module to send bulk email. I've specified in the mail system configuration to use the Corporate Clean theme. The customizations do not appear to cause the following problem since I can't see any color settings that reflect what I'm seeing with the problem.
The email that is received (via Thunderbird) is displayed with a dark gray background and light gray lettering. It is readable, although, I'd like to make it easier on the eyes. On my phone, it is unreadable - the text actually shows as black text on a dark gray background. I'm assuming that the color is specified somewhere in the theme or css. However, I have not been able to locate the settings that would allow me to change the color combinations. I've read a similar, but, old post but did not quite understand if there was a solution mentioned.
I'd like to get a better understanding of how to control the theme colors for email. Can anyone tell me how the colors are controlled and how I can change them?