Can anyone please advise, i realise the rule of thumb is that if the mucus from nose is clear, its all good to go to daycare, but what if its clear and then randomly a little yellow??

Lily was suppose to be at daycare, 30mins ago but i am furously trying to doulble check, i have contacted her daycare and just said if its clear then yeah come, but iam worried that its clear and then they may see a little random yellow and i ll be putting other kids at risk!