my hair looks much lighter in natural light

I’ve been perm dying my grey hair , a darkish brown , my hair looks great in indoor conditions , but if i go out into the sunlight my hair appears to lose a lot of its colour and looks almost a odd red colour , its almost as if my hair has become see thru ! , i’ve been using :- wella welloxon perfect 6% , 20ml koleston perfect 6/0 , 20ml koleston 5/0 and a bit of koleston perfect 6/1 . usually left on in a warm room for around 1 hour.

In the past it seemed to be ideal it worked fine , but for the past year it seems to not be so good , i've not changed my formula etc.

Advice please.