Grey out but show colors when hover or click

Hello - 

I am trying to set up a slide where the objects are initially greyed out. Then, when you hover over objects you can see the objects in color instead. Additionally, when you click the object the objects should stay colored, and a variable is going to be set up so that the selection will trigger jumps to specific slides.

Please see the image attached (from a training) that has this set up.

I haven't been able to find a good way to do this - played around by graying out the base layer and adding layers with the images in color instead that are triggered when the object is clicked. However, it wouldn't allow me to both have hover over or click to color.