It looks more like water entered the pool from either the drains or the returns, not actually through the plaster. But it's still could be bad. That standing water can leave permanent stains, as new plaster is susceptible to that. They're supposed to cap off all the plumbing penetrations while applying the plaster, to keep plaster out of the pipes and water off the new plaster, though I'm not sure how that's done with the type of drains you have. No matter, you're on the right track: a conversation with the PB. But you might bring up the possibility of staining and how he intends to correct it. If they do the typical post-plastering acid wash, that might be all that is required. Acid washing is done to new pebble, but shouldn't be done to new plaster (non-pebble surface). I'm guessing you have pebble, since I think with plaster they fill the pool immediately. Pebble they wait and do an acid wash the next day, then fill it.
Which is why I actually chimed in. This might be the last day your pool is ever 100% empty, so you have a unique opportunity. Just before they fill the pool, and you have to keep your eye on them 'cause it happens immediately after they're done, go out and read your water meter. Take a snap shot of the numbers. When the pool finishes filling (usually when the water reaches midway up the skimmer opening), turn off the hose and go out and read the meter again. The difference between the two readings will be the water volume of your pool. You'll probably find it to be quite different than what they told you it was going to be. Either way, you'll use this now accurate number for calculating pool chemical dosing, so the better the number, the more accurately you'll be able to dose.
You can increase the accuracy of the number by minimizing water use elsewhere while the pool is filling: turn off your irrigation system, take a day off from laundry and dishwashing, minimize showers and flushes, etc. The less water you use in and around the house, the more accurate your pool volume number will be.
Congrats on the new pool!
Edit: Awk! Mike beat me to it, because I was blathering on while he was typing faster!!
