I'd like to change the color of the grid lines of the calendar from a light grey to a darker color. I use the theme Dusk to Dawn. With Firefox's inspect I found out that the color of the vertical lines are defined in the custom.css under ".fc-widget-header, .fc-widget-content". However the color of the horizontal lines are taken from the ".entry-content td, .comment-body td" field in the style.css of the theme. I don't know which other elements of my website are affected by this field.
So what is the "cleanest" way of changing the colors? How do I find out which elements are affected by the above mentioned field in style.css?
Thanks in advance.