Good question, the "verify" option, where you could watch old of our image-colors signature, will only reveal part of the colors , (maybe will be pay-per reveal, and one part will be never revealing and other part random), so if somebody try to tamper with the archive will not work.
If someone is preper and he build a "strategy" (not so common) he could be recording the webpage stamp, and so yes it could kinda fake the timestamp video. because of that this works reliable for: trust something is live; or the video has the timeevidence timestamp AND he uploads it to a 3rd party social network (so 2 timestamps) the timeevidence video (is not old) and the social network timestamp ("uploaded today at..." so its verified in the now, also without time to tamper ). This is common rutine at "identity verification" or sending "rental conditions" etc
I think lighting is more to trading webs, if you want to transfer from bittrex to blockchain.info it would be trough light so all this kind of transactions would free the blockchain