Want to add some teal to my blue hair..

I minimise the bleeding when I have multiple colours by co washing. This is much less harsh fading wise and causes less bleeding between the colours.

Washing in cooler water would also help.

Co washing is conditioner only washing, so using conditioner as a shampoo. In case you're wondering 🙂

Co washing is conditioner only washing, so using conditioner as a shampoo. In case you're wondering 🙂

Haha oh yeah i definitely should have clarified that 🙂

Thanks for the help guys 🙂 I currently co wash about once a week and use a clarifying shampoo before I dye it. 
I've always been worried about using more than one colour incase they bled and I ended up looking a mess!
Think I might brave it and see how goes! 

I think you should be fine, if you co wash already you'll have minimal bleeding, and teal bleeding in to blue wouldn't look messy anyway so you don't have anything to lose.

As it's blue, any bleed wouldn't look bad anyway. You'd likely get nice graduations in fact. But what I do is make the area that I'm going to make a darker/stronger colour smaller than I actually want it to be. That way any strong bleeding shouldn't look bad.