May be the mage guild passive that increases the dmg of your next attack by 20% if you cast it in the next 5 seconds.

Would it be the nightblade ability siphoning strikes perchance?

There's a few things it could be.

Sap Essence/Power Extraction puts a faint red glow on a nightblade's hands to indicate the major brutality buff is active.
Reaper's Mark puts a red lightning effect on a nightblade's hands for 5 seconds to indicate the increased damage buff.
Leeching strikes puts a black/red glow on a nightblade's weapons while active.
The rally morph of momentum causes a character to glow a faint red.

By the way, forgot to mention I saw this in a mages guildhall, so it's not combat related, it looked the same as overload, just red.

You are most likely referring to the champion passive "opportunist, which increases your next physical attacks damage after interrupting an enemy. Needless to say for some magicka builds, who very rarely use physical attacks the effect hardly ever gets used up and results in orange glowing hands.

If it was in a non combat situation, it was either a graphic bug with a different buff, or siphoning strikes as it is a toggle.

i'm assuming it was an NPC. with a RED OVERLOAD, some NPC's have nice looking effects we cant have. screeny it if you can.

There is a 'buff' in East March that will reduce all damage taken player can get if they talk with NPC. Similar to old Grahtwood buff. The hands glow red while the buff is active.

If it wasn't combat related, I think the DK ability igneous shield does this to signal the extra healing done while its up. The glow is more orange-y than red though