Masonry Gallery overlay color and image

Hi, i am using a full width masonry gallery with pictures on a site im working on. But there is something im not being able to change with my CSS knowledge.

Im trying to make some images of the gallery to have a solid color on mouse hover, and others to have no hover.
And also, if i can make those with the solid color to work the other way around: to be displayed as a color when normal and when hovered, display the image attached. But the others with no hover, to display always the image.

i don’t know if it is clear.

Also: is there a way to make images on masonry gallery change place randomly??

Thnks!