Adding a hover colour overlay to image

I have created an image grid for this page and have added links to almost all of the images within this grid. I would now like to create a hover effect for each image before someone clicks on it.

I have attempted multiple CSS codes but to no avail, am starting to think that I have something missing in my html.

• This topic was modified 4 years, 4 months ago by malteser99.

The page I need help with: [log in to see the link]