Well while you guys who got them from Andy's have seen them get greener, mine (bought from a place in Germany) has got yellower. But then mine started very green so it could not really go the other way.
I have it in an almost south facing window (slightly south west) and over the summer I gave it some outside sunshine as well.
The window it's in is the brightest I have and will start getting the sun in early afternoon as it clears our neighbours house. Very little direct sunlight at this time of year as we are in cloud most of the time, but it got more earlier in the year.
Being mounted I water every day. Over the summer I was watering twice a day but I've dropped that back as the weather has cooled. I use fertiliser in the water once a week (ish).