Using a P3 document, with the Canvas set to P3.
Make an artboard with P3 color, export as PNG and untick the ‘Save for Web’. Observe that the colors match those in Sketch
Now export as PNG and tick ‘Save For Web’ and notice that the color is desaturated (expected)
Now export as WebP and you are unable to choose any option keep the color profile; resultant file will appear desaturated as color profile has been lost.
Is there any way to export to WebP and retain the P3 color profile?
Is there any update on this? We are currently having to author a plugin to export webP properly so that P3 colors remain intact. Would be good to have the ability natively.
Hello there @benfrain, and apologies for the belated response to this thread!
As you know (since the plugin you use does it), the webP format can contain the P3 information, so it seems we need to update something in our code to reflect this on export. I will speak with the team in charge of this in Sketch, and see what we can do!
I can’t promise any estimated time time, but rest assured we will look into this.
Cheers! 
I’ve been doing some tests running the command line version of cwebp library on p3 .pngs exported from Sketch.
Using the default config I get webp output very similar to what Sketch produces when exporting a webp. The secret sauce to getting vibrant colours that match the .png was to ensure the icc metadata was copied over from the png to the webp in the conversion.
Not sure if this will help you to solve the problem inside the Sketch app, but thought I’d share.
My final command to convert an image to webp with p3 color preserved:
cwebp -q 75 -metadata icc input.png -o output.webp