Classic High Voltage Semi-Permanent Hair Dye Blue Steel Blue Hair Dye Color Blue Steel is a cool, silver hair dye with blue undertones. For best results, we recommend lightening hair to the lightest level 10 blonde and toning hair that has yellow tones before use to avoid undesired hues. Semi - Permanent Hair Dye Fortified with Conditioners that Add Moisture to Pre-Lightened Hair Ready-to-Use Hair Dye Last 4-6 weeks on pre-lightened hair Available in 49+ Shades