There is some haze in the picture. 
The steps I would follow are these:

- Photoshop CC 2015 has a dehaze function that could remove it. 
- Then I would correct the color balance and remove some magenta and some Yellow. 
- Increase saturation 
- boost blacks and whites a little bit.

you can do all this also using the latest version of Lightroom, (also has the new dehaze function) or by using free software like gimp. Dont know how that works tough.