Kakashi developed purple lightning in the Kakshi Hiden novels, it was said that it was more powerful than his Raikiri and that it was solely developed to compensate his loss of obito's sharingan. There is no indication in the Sasuke novels that states that Sasuke is using purple lightning too, so i guess it's just SP with the fanservice. Other than that, i can assume that it's a manifestation of Sasuke's own chakra color, since we know that chakra color varies from user to user.
It's the color of Royalty.
Rikudou Raiton chakra is often coloured purple.
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How is it more powerful and compensate his loss of Obito's Sharingan? Is it more controllable? less intense and more powerful than Raikiri?
Purple lighting is bad ass let's all just agree

How is it more powerful and compensate his loss of Obito's Sharingan? Is it more controllable? less intense and more powerful than Raikiri?
It was purple in Boruto movie too and Naruto Rasenshuriken was yellow (the color of his chakra). That could be the case I guess.