I have just had the same dilemma re waterline tiles and I realised two things (if it helps)... Firstly it's the colour of the coping that I needed to match to, or compliment, the tile. And secondly, the colour of the tile matters if your pool is fully tiled, but if you are going with pebblecrete, then it's the colour of the pebblecrete that affects the colour of the pool and not the tile! First time pool builder, so who knew?! My fingers did do a lot of googling to decide on pebblecrete colours though. Good luck!

Barnes.... I actually know of a product that cleans that off with ease!!! It's new has had testing and has been through the process of intellectual property and is now currently under production. If you are interested I can try source you some.

it's never perfect and always involves a balance/compromise to achieve the less noticeable outcome - it's the decision with the convergence lines as to whether the base run is cut or the wall. That the wall run is cut it accentuates the pool fall more - if it was the other way around, in that the wall run comes down to a straight/horizontal line and the base is cut into that line the angle would not be as noticeable......you can fix it, and in this case arguably due to the window perspective looking straight on it's a justified request - adding water won't improve/soften the end result dramatically in this case IMO....that main thing is that it's been prep'd straight which it looks like it has been - this is only cosmetic remedial, which whilst yes will cost the contractor, you have to live with the end result so it's worth the (hard) conversation......good luck!

I quite like the idea of using same tiles as you have around edge of pool. Here are some pics to help visualise how it might look. The last one has almost charcoal coloured tiles, which would look pretty good as contrast to your lighter tiles and the blue waterline mosaics.