yes it can be done. Ive done it plenty of times. It kinda makes the color more shinier if its done right. I massage the color on first, then i pour the clear on top, then sit under dryer.....imo the clear rinse isnt gonna seal in any more than the color rinse. Its the same. Itll still come out during ur washes. I see no difference in the amount of time the color stays in my hair when i mix them or not. rinses in general can help seal the cuticle. The key to holding the color more is ur application,...and cuticles, & porosity......eta: i do mix different brands