"I see there are no longer any points left in the Gryffindor hourglass to take away. In that case, Potter, we will simply have to-"
"Add some more? I think Potter and his friends ought to have fifty points apiece for alerting the world to the return of You-Know-Who! What say you, Professor Snape?"
"What?' ...Oh - well - I suppose…"
-- Severus Snape and Minerva McGonagall (OP38)
The Gryffindor hourglass in the Hogwarts Entrance Hall for recording House Points is filled with red rubies (Pm, OP38).
- During Harry's first trip to Gringotts with Hagrid, he saw a goblin "weighing a pile of rubies as big as glowing coals" (PS5).
- The sword of Gryffindor is "ruby-encrusted" (CS13, CS18, HBP23). The rubies on the hilt are the "size of eggs" (CS17)
- The Gryffindor hourglass was shattered during the Battle of the Tower, spilling rubies onto the floor (HBP28).
- On the first train trip to Hogwarts, James Potter imagined wielding the Sword of Gryffindor (DH33).
- The tail lights of Sirius Black's flying motorbike are ruby-colored: "James and Sirius zoomed away into the night sky, their tail light twinkling behind them like a vanishing ruby." (PRE)
The color "ruby-red" is one of J.K. Rowlings favorite ways to describe a sky or sunset:
"The sky outside the window was ruby-red; it seemed to be sunset." (CS13)
"The sun was sinking fast now; the sky had turned to a clear, purple-tinged grey, but to the west there was a ruby-red glow." (PA16)
"Dumbledore turned back to look out of the fiery window; the sun was now a ruby-red glare along the horizon." (HBP25)
"The sky burned ruby" (TBB:FFF).
From ruber, Latin for red.