Finally: a rainbow hair trend brunettes can get on board with.

Image: Instagram (@auracolorist)

From Gwen Stefani to Nicole Richie, everyone’s been jumping on the rainbow hair bandwagon this year. Yet there’s one group who have had to watch forlornly from the sidelines: us poor brunettes.

Unfortunately, it’s a little harder for dark-haired women to spontaneously join in on the coloured hair trend. But that’s about to change, thanks to “oil slick” hair.

You might have spied this trend in your Instagram feed, and it’s largely down to New York-based hair colourist Aura Friedman. While an oil spill is probably the last place you’d look to for hair colour inspiration, Friedman argues it’s actually a very pretty look.

Mia Freedman has been contemplating going rainbow hair… but eventually settled for an edgy cut instead. (Post continues after video.)

“I’ve been trying to recreate gasoline or oil when it’s on the ground and it rains. I find that when you take a dark purple and a dark green and layer them one on top of the other, you end up with this iridescent feeling,” she told PopSugar.

It’s the perfect rainbow hair technique for brunettes because it actually requires a darker base to achieve the look. It also uses minimal to no lighteners or bleach, depending on how just how dark your hair is.

To transform her clients, Friedman usually does an Olaplex treatment to ensure the hair stays shiny and shows off the sheen of the dye. She then applies several different hair colours throughout the hair. (Post continues after gallery.)

Layering purple, blue, green, red and even yellow dyes, MTV reports her trick is to mix each colour with a tiny bit of black dye which gives it that “oil” look and slightly darkens the bright colour to make it more subtle.

Starting with the darkest shade at the roots, the dye is then applied freehand in alternating colours (and big quantities) to provide contrast, before being encased in glad wrap and then washed out.

The result? A delightfully iridescent head of hair which manages to be simultaneously very colourful and very subtle — and seriously shiny when the light hits it.

Edgier than pastel but more reserved than all-over rainbow, oil slick hair is the perfect middle ground… and bound to make the brunettes of the world very, very happy.

Are you tempted to try oil slick hair?