Highlight object on mouse hover

I followed a tutorial on creating a highlighted color on more hover.

https://www.youtube.com/watch?v=VHeem-mywDk

It works, however, the "mouse over color", doesn't look right. The material I have on the object is a standard shader with a texture attached. The mouse over color darkens it, but doesn't look true to the color I chose, for instance if I chose a light blue, it looks dark green. And yellow barely shows up at all. It's like its adding the color as a screen. I want it to be a bright highlight so the player knows the object is clickable.