Britney Spears joins the mermaid hair club!

Britney Spears has taken the "Coolest Mum Of The Year" award above and beyond when she dyed not only her hair, but her son's hair in a mermaid/merman colour.

She debuted her new mermaid-coloured locks in an Instagram snap when she took her sons Jayden and Sean Preston, and her niece Lexie to meet DJ Skrillex backstage at her Las Vegas gig on Saturday.

Brit responded to a fan on Twitter who pointed out Jayden's hair was similar to his mum's. The 33-year-old sent her fan a blue-heart emoji.

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Also joined by her brother Bryan, the Hit Me Baby One More Time hitmaker captioned her picture: "What a sweetheart! Thank you for coming tonight @Skrillex, dream come true for my boys!!"

The former teen-superstar also returned to her Las Vegas residency show, Piece of Me, on Wednesday and surprised the audience with a revised setlist.

To match her mermaid hair, Brit transformed Planet Hollywood’s Axis auditorium into a glow-in-the-dark dance party and performed her latest single Pretty Girls sans collaborator Iggy Azalea.

During the final minute of her neon-lit performance, Brit performed a raging dance routine, showing off her skills.

She posted a snippet of her moves on Instagram and captioned it: "Last night, SO fun!"

And of course, Brit isn’t the first star to experiment with vibrant colour.

Britney isn't the first to put crazy colours in her hair. She joins the long list that includes, Katy Perry, Nicole Richie, Rita Ora - to name a few.

And if you love Britney's hair why not take a look at these celebrities with rainbow hair: