One is not allowed to look at a Kohen's hands while he is performing Birchas Kohanim (source: my Artscroll siddur, but it is well-known too)
Would this also apply if one was looking at a video of the Cohen? (or a picture?)
The prohibition seems to refer only to the time that birkas kohanim is actually taking place (Shulchan Aruch - Orach Chayim 128:23) and to serve the purpose of allowing the onlookers to maintain focus on being the object of blessing by standing at attention and looking down. Though one should always COLOR, this would imply that watching a video would not detract from the purpose of averting one's eyes and therefore be permissible.