Warning: Possible spoilers for the movie 'Lucario and the Mystery of Mew,' possible spoilers for Subspace Emissary. You have been warned.
Red
Lucario's eyes could be described as red, but what shade of red was what got the Smashers confused. Some argued it was a red like the sunset, while others argued it was like the colour of blood.
It was really, really difficult to figure out an actual shade to identify with the aura pokemon's pupils, so this debate kept continuing.
Lucario had his own opinions, though. If there was one shade of red in existence that did not match with him, it was the shade of red that occupied the eyes of Tabuu, that rainbow-winged being that ruled over Subspace.
Those eyes, filled with such hatred, such passion to engulf every world in existence into Subspace; Lucario couldn't stand to think that the shade of those eyes could look anything like his own eyes. He refused to believe that it could look anything like Tabuu's own eyes.
At least, until one day when he seriously hurt Wolf during a match.
He'd been keeping his own self in check, staying as calm and focused as always, when Wolf just had to bring up Sir Aaron. He just had to bring up how Sir Aaron practically abandoned him, right in the middle of trying to rescue the kingdom and-
Lucario just snapped right there.
Wolf hadn't meant to rile up the aura pokemon. At the back of his mind, Lucario knew that.
But he just couldn't stop scratching and punching and flinging aura spheres at the Star Fox rival. He just. Couldn't. Stop.
When Marth and Link finally restrained the jackal from doing anymore harm to Wolf, Lucario caught a reflection of his eyes in the pooling blood.
Just for a moment, he thought he saw a flicker of the same eyes Tabuu had. The same, same flicker of those eyes of hatred, enbedded into Lucario's own eyes...
Since then, Lucario was really unsure. Perhaps, maybe, just possibly, his shade of eyes matched the ruler of Subspace's own?