What effect is this?

In the intro, it sounds to me like the guitarist is playing 1/4 note chords, with a delay filling in the eighth notes, with some high end roll-off in the delay repeats. That would explain why each quarter note has a stronger attack, and the tone softens with the repeats.

Yes - it sounds to me like the delays are darker sounding than the guitar tone.

Just to add my .02 - I almost always use some high cut and low cut on the delays. It makes them sound much more musical and sit better in the mix.