My hair is color light blonde and I have highlights two shades lighter . I also have 2 inches or regrowth . My natural color is medium brown . I want to color my hair a light brown but I know that if I apply the color I will have different colors because of the colors I have already. How can I get the color I want doing it myself. Thank you.

Yes you will have different colors. You need a color professional to fix that problem. If you use a box dye your hair will have lighter and darker colors. It may look cute like natural highlights though