I use the gradient function of MMM-BackgroundSlideshow and have made many adjustments in custom.css. First of all, I made the dimmed text colors a bit lighter:
:root {
--color-text: #e6e6e6;
--color-text-dimmed: #f5f5f5;
--color-text-bright: #ffffff;
}
They can also all three be given the same bright color, e.g. #ffffff for white.
Then I checked each module to see if it used the default fonts, font-weight, and text colors. If not this was changed. For the default calendar, the times were a little darker than the event title. Here are my adjustments:
.calendar .time {
color: var(--color-text-bright);
font-weight: 400;
}