need to be red reflectors to be uk legal which is why theyve included stick ons in the box.
years ago i used to have something similar on a car i owned, the rear lights were black without a reflector. at mot time id stick the reflectors on the bumper, pass the mot then take them off.
couldnt be doing with all that nowadays, not worth the hassle. point being is that if you want the lights as they are, dont bother with the stick on reflectors until the mot. otherwise you might as well have bought oem led lights.