Thank you. Model 20135-0427D-18.
It's silver. I think the photos look dark because it's brushed stainless steel instead of polished stainless steel and the light reflects differently. In person, it is silver with some shine.
I believe 18" is the minimal recommended length for ADA compliance vertical installation.
It is not adjustable. I installed it at an angle and it worked fine.
I would drill holes first so you don’t the break the tile
I would estimate 3 1/2 inches.
The product you are looking for with the escutcheon already included is Store SKU# 240200 and found here, https://www.homedepot.com/p/Glacier-Bay-24-in-x-1-1-4-in-Concealed-Screw-Grab-Bar-in-Brushed-Stainless-Steel-20135-03202-24/206767724
HomeDepot carries this product in white.
Although your question is almost 2 years old, yes, HomeDepot carries this item in white.
Yes. I used these bars on tile and there were no tile chips nor damage to the tile.