Is there a way to add a permanent colour overlay to thumbnails

Hello,

I have used yellow as the primary colour on my site and wondered if there was a way to add yellow colour overlay permanently (rather than on hover) to the thumbnails. 

The photography is all slightly different grades so want to make them uniform.

Thanks in advance

Hi,

What is your site url? We can check easier

Hey Site URL is - benandlewiscreative.com