One little known fact is that there was originally only one ranger, not five.
His name was Zor'iln Rerdon, and his suit was white.
He fought off the darkness endlessly, working to keep Rita Repulsa and her forces at bay for just a little bit longer. But one man could not fight forever, and Rita got the drop on him. Her spell sent him hurtling through dimensions until his trusted helper, Alpha, reached him. Zor'iln recognized the danger his absence posed and used a chunk of his power to split the white powers into five - much like a prism separates white light into a rainbow. He drafted five extraordinary humans to fight for him, and they managed to seal Rita away at a heavy cost.
Over the millennia, the humans' whispers simplified his name into Zordon, which he adopted.
He never forgot his old adversary, and his old powers itched for the fight. He found himself constantly looking and waiting for the pin to drop - Rita would return, he was sure of it. Alpha called him a paranoid old coot and told him to stop looking for a fight. But he watched, and he waited. He found himself returning, mentoring, constantly looking for the next fight.
So, when Zordon uses his powers to make Tommy his new white successor, he laughs at the irony.