change text colour "next" / "prev"

Hi, I′ve gone through the stylesheet again and again but I didn′d come across the proper place to adjust the colour of the text “next” and “previous” in the month-cell.

Originally it′s green but as I changed the background colour to that very same green, “next” and “previous” are no longer visible.

I′ve added colour:#000000; to the following section, but it didn′t help:

.calendar-prev {
width:20%;
text-align:center;
border:none;
}

Is there somebody out there who can help?

https://www.ads-software.com/plugins/calendar/