I think the white is because it's suppossed to be a "sand" castle. I think the idea is to blend it into the existing play area. Hopefully, Disney Imagineers can come up with a material that stays clean.
Wherewill this pool and slide be located? Are they revamping the existingMain pool area by Turtle Crawl(walk?) or will it be located next it where the sand and kids play area is?
Nezy, it's going to be built over by the sandcastle play area. I think they are doing some design work rather than just plopping down the slide. That's why it will take a few months to get all the work done and why they need to close down the pool.
Goldi -- I found a pretty good shot of the play area in this link. It does have existing white sand castles. Has anyone seen whether these show the dirt?
Luckymommy2 -- I hope I didn't give the impression anything is wrong with OKW. Disney has just decided it is time to add a slide to OKW. Now, all Deluxe and DVC resorts will have pool slides.
The above link also has some photos of the 2nd largest pool area -- Turtle Pond -- down toward the bottom of the link. This is only a partial view of the whole area.