Weird how horizon also does the weird green window tint.I have found in forza 4 that if you customise the colour of the car using contrast and brightness then the windows automatically tint green.
This might be because I took a picture of the tv screen with my phone but I see what you mean, it does look a little on the extreme side for 'non tinted' windows..
Horizon is worth getting just for the mini, I'll upload some pics of my '177' Monte Carlo replica one.. That on the mountain roads at the west of the map Plus C & B class online can be dominated with these little beauties