Using color picker in Blender, and copying hex and rgb to ThreeJS but the colors aren't the same?

Here’s a JSFiddle:

It looks like the RGB triplet you provided is sRGB (assuming it’s meant to match the hex code), but three.js and Blender both assume that RGB triplets are in the working color space, Linear-sRGB.

The equivalent Linear-sRGB RGB triplet would be .25, .982, .965 or you can specify that the RGB triplet is sRGB with:

color.setRGB(.537, .992, .984, THREE.SRGBColorSpace);