colors images change when hovering over images in how it works pattern

Hi Team, Sorry for another ticket. I change te icons in the "how it works" pattern. This was not a problem. Problem is that oil I hoven with the mouse over an image, the colors almost disappear, image becomes mostly white. It is as if I look to a kind of an image negative. The url is leusden.hagmeijer.nl Kind regards Hans Hagmeijer