Lighten Gray Hair
Q: How can I lighten the dark parts of my 75% gray hair? There's no way I want to try and cover all that gray, but I would like to make what's left of the dark blend better.
This sounds like a really simple answer, and it is. The results of attempting to lighten the hair are going to depend largely on the starting shade of the hair that is already pigmented. Some hair when it is lightened takes on undesired tones depending on the contributing pigments of the hair. Some peoples' hair gets very reddish, and some become orange when lightened.
Then there is the problem of dealing with potentially overstressing the hair in trying to lighten it. Even the gray hair with no pigment can be damaged by bleaching unless you use care. If the remaining pigmented hair is clustered in areas so that you have patches that are darker than others, you could use a foiling or cap highlighting technique to isolate the darker hair in order to lighten the overall look of the hair. If your pigmented and gray hair is evenly dispersed throughout the head, this isn't as viable a solution.
Seriously, my best advice is to speak with your salon stylist about the options he/she recommends for your hair if you only want to try and lighten the existing pigmented hair. Without being able to see your hair and know the exact pattern of gray vs. pigmented hair, I can't be sure how would be best for you to proceed.
That being said, and understanding that you have said you didn't really want to try to cover all the gray, you might consider using a high-lift color formula with a pale blonde color to lighten the pigmented hair and add a little color tone to the gray hair. You would have to do regular retouching of the color, but you would need to do the same if you simply lightened the darker pigmented hair as well.
How does bleaching hair work?
How to highlight hair with a highlighting cap
Can I increase the progression of my gray hair?
Can I use a product to remove my hair color and go all gray at once?