If you want a temporary hair dye for a specific night out, holiday or weekend then these are the products for you.  All of these gels & streaks are one-wash out hair products.  As with all semi-permanent dyes they will not lighten the hair and will only show up vibrant on light-coloured or bleached hair.  Some of the stronger, darker shades may give a hint/shine of colour on unbleached darker hair shades but this cannot be guaranteed.