I know that developer and color that is mixed cannot be re-capped and used or it will explode. But if I mix half the developer and half the color, can I recap the unmixed for use at a later date? Or will the fact that it has been unsealed ruin the effectiveness? Sometimes I just need to touch up my temples and the rest is still fine. It seems such a waste to throw so much away. If anyone could answer I would appreciate knowing.