I'm with Patty. She is being WAY over-the-top inappropriate and it's time to fight back. I'm liking Team WTF is Your Problem, myself. But Team How Sweet of You to Notice is good, too.
Actually, that might be good. In psychology it's called "reframing." Instead of thinking "Oh, man. I have to put up with Former Boss being horribly inappropriate with me and I don't know how to defend myself, and it's just awful," you think to yourself "I'm going to the store and Ol' Jerky Former Boss is going to do her Jerky Thing, and this is how I'm going to handle it." And then you DECIDE what you are going to do.
It sounds like you aren't the confrontational type, so you might want to experiment with Team Kill Her With Kindness. At this point it's become a pattern. Next time she makes a remark about your hair, you can pick one of the suggestions here, and say:
"How sweet of you to notice!"
or
"Yes, I just LOVE this color!"
or
"It always brightens my day when I come in here and you pay such close attention to my hair color!"
And no matter how she responds, you can keep repeating something similar, all the while being inwardly amused that she is so obsessed with this issue that is none of her business.
Or if you think she has really crossed the line with the touching, if she tries it again, you can be prepared, and grab her by the wrist, look her straight in the eye, and say something like:
"Sorry, no touching!"
or
"No touching. I have cooties."
or
"No touching. I don't know where your hands have been!"
or
"No touching. I mean it."
Repeat as necessary and I bet she will be speechless.
Good luck! You can do this!!!