help with coloring

Hi, I'm new.  I have very "old" looking blond hair-dark and dull unfortunately.  I used to do an all over lightening thing with Hydrience and it did great, looked nice etc.  I wanted to get away from the "too blond" thing recently and used a L'Oreal product which is a sort of a cinnamon color with blond highlights and I absolutely love it although it is fading.

I think I had a very mild reaction to the L'Oreal product, had an itchy scalp for a week or so after coloring so I'm expecting a mild reaction again and will live with it as long as it doesn't get any worse than it was...would slathering my hair and scalp with porosity neutralizer help with that?  Will that help it hold the color longer?

Thanks in advance for any ideas...I loved the color so much I really want to continue to use that product but would love it if it will not fade so much...

Thank you Karen.....