If you need a uniform array, use uniformArray(). E.g.
const tintColors = uniformArray( [
new Color( 1, 0, 0 ),
new Color( 0, 1, 0 ),
new Color( 0, 0, 1 )
], 'color' );
If the array data are constants and don’t have to be uniforms, you have to wait until the following PR is merged: