I'm about to embark on a journey to remove my existing dark auburn dye from my hair and then plan to dye it a lighter orange-red kind of auburn. My natural hair is a dirty gingery blonde and I've been considering using a mix of Cajun Spice and Paprika to achieve this colour (ideally without bleaching my hair once I've removed the existing darker dye). Would that work on unbleached fairly light hair?
It should do (though it does depend on what fairly light hair means to you!), but it won't stick well to the roots as the parts that have been dyed previously grow out. You should probably do a very weak bleach bath or presoften your hair to give it just that little bit of damage to help it stick. You just need to roughen the cuticle slightly, so it'll still feel the same to the touch.