Nicnik,

I'm sure you realise, but I'll just say it for clarity...
Although they're called white glues and they go on your head white, they turn clear/transparent as they dry.
They can take 5-15 minutes to turn clear and you can apply another layer or do your attachment.
After that, to fully cure & harden, ideally they need 24 hours in which they don't get wet or the scalp sweats.
If the glue does get wet in that time, it turns white again.
Other than that, white glues are invisible.