white background converted in #fbfbfb

MP4 will compress colors, give you imaginary frames must be interpreted before for playback and is NEVER a suitable professional format for any kind of digital intermediate. Use a suitable frame based production format and you will get far better and more predictable results. The same workflow works but the most efficient workflow is:

1. Make sure there are no duplicate frames in your AE comp - if the action freezes for 10 frames remove 9 of them (i will explain later)
2. Render a suitable Digital Intermediate - easiest, use the default Lossless or Lossless with Alpha in the Output Module/Render Cue
3. Open the DI in Photoshop and make sure you are in the Motion Workspace
4. Set the timing for any frames you want to have no motion (that's the explanation)
5. Export your Animated GIF from Photoshop.

Using this technique you could set up an animated banner add that had 4 slides with a half-second animation between each slide and held each slide for seven seconds that was only 32 frames long. If you left out removing frames in AE (easy) or deleting duplicate frames in Photoshop (much more time consuming), the same GIF would be at least 135 frames. That's a huge difference in file size with absolutely no reduction in quality that you get because you can tell an animated GIF to hold a single frame for as long as you want it to hold.

The use voice thread has 8 votes.  I’ll see who I can wrangle up to get that number increased.

-Warren

The "correct" answer was how to fix the off-white in the resulting GIF, not how to avoid it in the first place.

I made my gif by using the Video Timeline in Photoshop CC 2019 and then exported it as an mp4 (only available option- NO GIF EXPORT!)

I ten took my mp4 through Adobe Media Encoder to get it saved as a gif.

Checking that gif back in Photoshop showed that the white background had changed to #fbfbfb (transparent gif background was not an option).

As the gif is not in indexed colour the colour table trick to correct this is not available to me (greyed out).

Change to Index colour flattens the gif layers.

Unfortunately, no, CC2019 does not resolve the with 100% while backgrounds (255, 255, 255 or #FFFFFF) shifting to off-white (251, 251, 251 or #FBFBFB) when exporting from After Effects to Adobe Media Encoder to an Animated GIF file.

I've embedded a GIF that demonstrates the ongoing issue:

I've had good results from GifGun which, of course, would not be necessary if AME worked as expected: GifGun - aescripts + aeplugins - aescripts.com

Of course, going to Photoshop still works.

There are a four items under "Animated GIF" on the Adobe User-Voice for AME, but none address this issue.  Not only does the shift in white need to be addressed, but it would be amazing to have the same settings that Photoshop has for exporting to a GIF file.  Once you get used to that, it's kind of hard to come back to AME.

-Warren

Thanks again!

For what it's worth, GIF export on Mac is back with the latest release.

Also, I'm 99% sure that the bin hex value FBFBFB is not available without loading a custom indexed color palette (in this case, an "exact" custom color table).  That or the export options would have to allow for exact colors.  I haven't played with the GIF options from AE in a long time as the feature was discontinued on Mac.  A good 20 years ago, you would load a custom color palette when queuing the render (having saved the color table as an ACT file from Photoshop) to avoid getting the Windows default color table or Mac default color table.  Sorry I'm not up to speed on the latest options.  Hopefully, someone will chime in.

When saving in Photoshop, the Indexed Color options allow you to choose "exact".