Illustrator :: Convert Complex Vector Object To Greyscale

I have a complex vector object, containing of forms of all kinds and what not. They have two colours: black and red. To use this logo in a background area, I need to make it all grey. Everything which is black or red shall then be light grey or so. But the appearance panel can't do a single thing. It just says "this is a group, I can't handle that". So I ungrouped the entire object, then there were other sub-groups. I could go on ungrouping everything forever, but that can't be the solution. When I just click on a colour in that colour panel instead, it sets the outline colour of every single element. It hasn't always done that, there were times when it would set the fill colour of all elements. But there's no switch to tell it what exactly to set. Should I way until an even or odd day so that it would set the fill colour again?

Illustrator CS6 on Windows.