Washed out desaturated colors after export in Quicktime/Vimeo

The first step in quality control is to ensure you're seeing the image accurately.  That means getting it off the computer and onto a calibrated TV.

How it looks there is all that matters, all that you can control.

"You can't fix gramma's green TV."

That's from a colorist talking about Live as a Pro Broadcast Colorist. He'd graded a major-company commercial, it looked hot. Went to Wisconsin to visit his gramma, one of those who leave the TV on all day in the background. During the visit, "his" commercial came up.

Looked horrid to him, of course ... but to gramma, it was awesome. Because ... everything on the TV of hers looked the same off-green color/tint because of the horrible settings used. Being as everything she saw ... all pro broadcast stuff, remember ... was like that, his ... relatively ... looked perfectly excellent and professional.

The lesson of course is you set up your gear to produce as close as possible to full pro broadcast standards. And ... let it go. As "Out in The Wild" you have no control whatever. Every screen will be different. One moment someone on a phone will be in bright sun, the next, darkened room ... and that has a massive change on how stuff looks on that screen. That phone won't be at all like any of their computer monitors ... who won't be that close to each other, even the same monitors on similar computers.

The bane of colorist's is the client-attended grading session. Understand, colorists have many-thousand-dollar specialized monitors, fed by external boxes that have LUTs created by many-thousand dollar calibration systems. Both for their grading/reference monitor and for the big client monitor "over there" with the cushy seating. At some point, client gets up to stretch, sees the colorist's monitor, which can't possibly even with that level of calibration be exactly the same as the client monitor ... client gets up & says ... "Make my screen look like that one!"

There is absolutely nothing you can do to match that client's view to your screen exactly, or even have any guarantee it's going to be that close. Period. I do suggest you inform your client that you cannot accept comments about saturation/tonality from viewing in QuickTime, but even if they do use VLC or PotPlayer, if their OS/monitor/player aren't properly set up, they will not see a correct view of the image anyway!

The new Macs have wide-gamut P3's, and fairly poor options apparently for displaying the correct color space for video standard sRGB material, so that's a bit of a battle to begin with. But what the heck, Apple/PC, you'll be sending to people with middling to terrible monitors and they will not be off the same, so you cannot outguess them. If you go one way it might look better on some systems but will be worse on others.

And then ... on no system will your work look relatively like pro broadcast quality work. Personally, I don't like this option.

What you need to worry about isn't whether it looks like your screen ... it's whether it will look like b-cast standard pro work relative to other b-cast pro work on those screens.

As far as web work ... Chrome & Safari are nearly as bad as QuickTime player for ignoring color tags/flags in media they play. Firefox, like VLC and Potplayer, does recognize and observe media color tag/flag settings.

YouTube ... often skips the second encode that correctly 'shows' video media. You can force that by going to your channel, selecting a vid, going to the modify/retouch (whatever it's called) space, then just save without changing the image. It will then re-encode to a better, more appropriate view.

Or ... you can use either Cineform 10bit YUV or DNxHD/R to export your media from PrPro, then upload that. YouTube will take them, and they seem to get displayed more correctly than most H.264 unless you force the re-encode. The files are bigger so the upload is slower, of course.

I'd recommend using the Cineform/DNxHD/R option to upload, and provide your client with a gentle letter informing that for best quality, use of Firefox browser and VLC/Potplayer for viewers is recommend ... and that you cannot recommend Chrome/Safari and YouTube player. As a professional courtesy.

Oh ... are you using the Preferences option to "enable display color management" ... on a newer Mac, you should try that, it may help.

Neil