Leonardo said:

I'm color blind

^ There is your answer dude ;-)

But seriously, the red is a little less saturated than I remember in that YouTube clip but it was never that bright to begin with. Probably a YouTube encoding thing as you say.

Additional: Shot from Blu-Ray.com...

Back in the day, I saw it in RE class on VHS too and remember the red being a touch stronger. Perhaps it was boosted a tad for the VHS release to compensate for the loss in "resolution"? Because in most shots she is just a dot in the distance.