To echo was @Lava Lamp Freak has been saying, as well as what The Verge said in their review today, the "washed out" colors we are seeing are the result of the Pixel displays being sRGB calibrated. This is good for the fact that the colors you are seeing are in fact the TRUE colors that the app developers, web designers, etc., intend for you to see. Now, whether or not you prefer that is a different story. I prefer the saturated colors, but I digress. I'm probably just too used to my Nexus 6P's display.
But what I saw was only sRGB in Chrome. All other apps looked more saturated than my S8 in basic mode. All of the colors from icons, Gmail, Google Music, YouTube looked much more vibrant than they do on my S8. I actually feel like my S8 looks dull now. I liked that extra saturation. But as soon as I change to anything above basic on my S8 it doesn't look good. So, I really liked the added saturation on the XL 2 because it looks like it is saturated by design rather than as a byproduct of changing to a different color gamut. But I think we can get used to differences in saturation, so I don't think you'd notice after using it for a short period.
And a year from now I don't think this will even be a discussion any more. Considering iPhone X is doing the same thing as Oreo, I'd bet that all of next year's flagships are color-managed automatically and we don't even need display modes any more.
[doublepost=1508293037][/doublepost]Oh, and for anyone interested in buying from Verizon, the salesman tonight told me they have a room full at the store I was at. He didn't think there would be any stock issues for Thursday's launch.