Ok let’s hopefully answer your questions for you.
Firstly long curly/frizzy hair can be thinned, either by having long layers cut in (but this can create more volume if the layers are cut too short) or you could have your hair thinned using either thinning scissors or a feather blade. Both of these will help reduce the weight in your hair and hopefully reduce the volume and frizz.
I also would strongly advise investing in some Sebastian Potion 9 which is a leave in conditioner/ styling product which is fantastic and calming frizzy and curly hair. ...More >
Right onto the colour.
This is a little more tricky, as it sounds like the problem your hair is VERY resistant to colour. Unfortunately lighter shades are going to have little or no effect on your colour which is why they end up having to use darker colours.
These are only suggestions and are not guaranteed to work but firstly I would advise an appointment with an Wella MCA/MCE graduate, who is an expert in colour, and also perhaps they may suggest ’pre softening’ your hair to help with the resistance and there is also a specific range of Wella colours that are for resistant hair which should be worth a try.
Hope this helps.