How old is he? Is that him in your avatar? If you have only had him 5 days he is probably still settling in. Are you misting him twice a day as well as providing the dripper? Is that the first time he's pooped since you had him? If so then a little yellow in the urate is ok. The longer the urate is held in the body, the more water gets absorbed from it, thus making it yellow. You will notice that the last bit to leave the body is always very white. My male Veiled would only poop every week or so and he always had a little yellow/orange at the start of his urate, even though he drank at every misting and more in between. I would try giving him longer misting sessions for a couple of days and see how he does. Sometimes it can take a while for them to realise they should be drinking when you mist. It doesn't need to be constant either - leave a few seconds between squirts and the cage doesn't get so wet either!