change link color of title-thumb in theme "spun"

hi there,

i’m using the wonderful spun-theme at my website theresabergens.de and have made several changes using a child theme.
What i couldn’t figure out is, which css-command i have to apply in order to make the thumb-titles (in my case the light red ones in the circles) on the startpage change their opacity to full or change their color on mouse over and when the link was visited?
so far i could only find where to change their color and opacity entirely…:>
thanks for any help and hint!