can i mix two shades of clairol perfect 10 by nice 'n easy?
short answer: yes. now for the caveats: be sure to pick two colors that are close to each other (i mix "light auburn" and "dark auburn") and that have the same undertone -- warm shades should not be combined with cool shades.
how to mix two clairol perfect 10 shades: set aside the color activating creme from one box (you will only need to use one, but since you bought two hair dye kits you have two). now pour approximately half of the high gloss color creme from your first selected shade (ie: light auburn) into your bottle of color activating creme. take your second shade (ie: dark auburn) and pour half of that high gloss color creme into the same bottle of color activating creme. shake well and apply as usual.
bonus: you now have one color activating creme and half of two tubes of color set aside to use for the next time you want to color your hair.
i've been using this technique to customize my hair color for over a year, and beauties, even hairdressers compliment me on my at-home color.