You're using the default style of the tiles, but you want the title/description background to be more or less transparent?
If you want to change the transparency to a darker version, you can easily do it by using some Custom CSS as follows:
.shortpoint-tile-content { background-color: rgba(0, 0, 0, 0.8); }
And for example if you want it to be less transparent
.shortpoint-tile-content { background-color: rgba(0, 0, 0, 0.2); }
Basically the last number in the code above represent transparency
It can have a value between 0 & 1
1 means it is solid and not transparent at all
0 means it is fully transparent