That milky look is homogenized oil/water.You might wanna>warm up engine>drain drain transmission,,let it sit a several minutes draining.>put a whole quart of ATF(Automatic Trans Fluid) which is overfilled.>ride it GENTLY a few minutes>Drain the ATF,,,let it drain a few minutes>If by chance it's still milky,,,Do it again---yeah,it's a nuisance to do it twice.But it's easier than changing trans shaft bearings in a couple months.Refill with proper level of whatever trans oil you're gonna run.I use ATF in most wet-clutch gearboxes,like your KX.