Talk about showing your true colors.

The Bluebelle ($5.75), served at NYC’s temporary outpost of Thai eatery Kay’s Boutique Cafe, is a bright-blue drink made with coconut juice and bluebell vine flower tea.

But things get crazy when you add a squeeze of lemon: The drink transforms from its original blue hue into a vibrant shade of amethyst; apparently, the acidity of the lemon triggers the tea’s alchemy.

Chef and owner Pavitra Kobkulsuwan, who’s running the Kay’s pop-up at 240 Mulberry St. at Prince Street through June 30, chose to use the floral tea because bluebell vine is a popular flower in Thailand.

“It’s just unmistakably striking,” Bangkok native Kobkulsuwan tells The Post. She loves that its “wow factor” is “directly from nature.”