I'm dumb: please explain the CC UI to me

[Loggos]

Oh wait, that's the blue glow OP meant. Sorry, I completely missed that because I was looking at the blue progress bar on the other side (got confused since coincidentally the crystal went from no-glow to glow in the second picture too and thought that's the glow that was referred to). orz
(But that also goes to show how unintuitive the UI can be, if the info for your team is all over the place. I get that the progress bar is supposed to mimic your path from your base away towards the enemy base but for UI I think consistent visual grouping can make more sense.)

I checked some recordings again and the colour pulse (as in AmiableApkallu's screenshot) indicates the team that's currently ahead.
It's also unaffected by who is on the crystal.
So if blue is ahead and nobody is on the crystal, it will still pulse blue. And if red recaptures and pushes the crystal in the other direction the blue side will still pulse/glow until red overtakes their progress.
If progress is even, there's no glow/pulse on either side.

I have no idea why there's no glow in the first picture of OP's post because it should be there since blue is ahead. Maybe it's an oversight or they took their screenshot in that short moment when the pulse fades before it returns.

[Valence]

So it means that this picture is doctored and doesn't represent anything or actual gameplay since a team is clearly ahead but nothing is glowing

[Loggos]

Yeah I think so. I guess they just messed up here/didn't pay attention to this detail.