Green tinted hair after mixing 2 blonde shades

Hello,
I'm 17 years old and in November 2013 I went to a hairdresser to get blonde highlights put into my home dyed brown hair. At Easter 2014 I decided to then go fully blonde home dying it and used an Ash blonde first and after a week used a second shade of blonde, it then took me one more stage of dying to get to the preferred colour I wanted. What had happened was the ash shade reacted with whatever other shaded I added or had previously got from the hairdresser and turned the tips of my hair a greeny colour. I ignored it and carried on dying my hair a bright shade of blonde, avoiding the ash shades, every 4-5 months when my roots were over showing. I had alot of my hair cut short to get out the green but still some showed, I tried home remedies such as baking soda and shampoo which worked for a while , I also tried egg and lemon and all sorts which didn't make a big enough difference in the first 2-3 goes which made me give up. Eventually in March this year I decided to just dye my hair red and still have it now at its faded -whiteish stage since I havnt dyed it since the first week of July. Sorry for so much detail but now what I would please like some help with is, I've wanted to go back blonde but have been waiting to go either into a salon and ask them the best way to do it or just do it myself, I'm currently on holiday in Portugal where I have been impatient and found one store here that sells box dye and have put highlights in a couple of places of my hair. I like it and its come out nice only for a little orangy tones from the red I can just use toner on, but on at least 2 of the highlights I've noticed a very faint greeny\blue colour to the tips that I think will be more noticeable when I decide to do my full head. (Back when I was blonde nobody really noticed my greeny parts unless I pointed it out,but it irritated me) so please ,if you've got any advice that could help, I looked up numerous websites and tried so much and was really disappointed seeing the greenish tones when taking the tinfoil off yesterday. I'm really sorry for such a long message just for this is my last resort and I'm making sure you fully understand. A big thanks to taking the time to read this and I hope there's some sort of way of fixing it instead of chopping it off! One last thing is I'm going back to school next week and would like to skip that awkward orange to yellow to blonde stage,if a hairdresser can get it done in 2 stages I would go for it ,thanks again!

Your sincerely,
Ruby