My guess is that it's to make him look non-Han, part of the "Europeanized" Haixing world-building.

At first I thought characters with hair that isn't solid black are always Dixingren, Yashou, and Hanga (note Flower Lady and Da Qing, above). It often goes along with earrings for men, elaborate earrings for women.

But Lin Jing *also* has lightened hair, so it can't be that.