Do you have any explanation & suggestion to my problem? I have been highlighting my hair since I was 19 (my original color was dirty blonde/light brown). At age 32 I am almost half white/gray haired and my natural color has darkened a bit. The problem is that my hair is no longer taking/accepting the highlights or color. Instead of blonde it turns orange now. Even highlights take forever, which can burn the hair, and still comes out slightly orangy instead of the golden blonde I used to be. Do you know why this is happening and how I can become my old blonde self again? Any suggestions would be greatly appreciated!

This is probably because of the graying of your hair. Highlights look different when applied to gray hair & blonde hair. I would suggest you do opt for a darker color since your hair will be harder to dye when graying.