After the death of Zeon Zum Deikun, his wife Artesia entrusted Zeon’s children Casval and Artesia to the care of Ramba Ral, who stole the children away to Earth. Ramba Ral sent the children into exile with his father, Jimba Ral, who was stridently opposed to the Zabi family then in power in the Autonomous Republic of Zeon.
Jimba Ral instructed young Casval Deikun in politics. In the Mobile Suit Gundam: The Origin - Eve of The Red Comet TV series, episode 3, Jimba lectures:
When he realized the historic duty of Spacenoids and codified the reformation of mankind into an ideology, that was when the grand concept of ‘Newtypes’ came into being! In every age, prophets have been solitary figures. Even Deikun’s ideology was not readily accepted by the masses at first, and …
It was only when humanity went into space and was able to view the Earth as a living organism that a time of evolution came upon us! It is newtypes, who will not only transcend imperfect communication and achieve true mutual understanding, but will also gain new physical possibilities, who will be this world’s …
— English subtitles, 9anime.to version
The lecture is cut off at those ellipses, but it’s enough to get across the part of the ideology of an early Zeonism. It encompasses Earth as a living creature, and space as a transformative environment for humanity. That potential for transformation was central.
Ramba Ral inherits his father’s loyalty to the Zeon family. With the smuggler Crowley Hamon, Captain Ramba contrives Casval and Artesia’s escape from the Principality. His plot is discovered, and for three years he leaves the military.
In UC 0071 he rejoins the military as a mobile suit test pilot. In 0078 he participated in the first mobile suit conflict during a covert action to recover an defecting Zeonic scientist, and received a two-rank promotion to commander for his success. When Dozle Zabi briefs Commander Ral on Operation British, the plot to gas the occupants of a space colony before dropping the entire colony on Earth to destroy the Federation’s headquarters, he refuses.
Dozle Zabi: The opening fleet battle was a resounding victory! We sure showed Revil how it’s done! What’s with you? Why the long face? Can’t you be happy about our victory?
Ramba Ral: If I had my druthers, I would rather have fought in the fleet battle. Hatte’s forces are of no consequence. There was no need to declare war on them.
Dozle: Don’t talk like that.
Ramba: That’s Island Iffish, isn’t it? We could have taken it in half a day if we felt like it. We were ordered to leave it untouched, though.
Dozle: That’s precisely why I called you here. Brilliant man that he is, Supreme Leader Gihren came up with an ingenious plan. A plan to end this war with victory for us in one fell swoop!
Ramba: We’re going to murder the citizens and drop the colony?!
Dozle: Shh! Don’t use that word! It makes it sound like we’re doing something bad. [He orders some soldiers to leave the room.] Look, this is war! We declared war on Hatte, an enemy country, and we beat them!
Ramba: Even so—!
Dozle: Let me continue! Take a good look at this! We’ll attach external engines to the colony, take it out of orbit, send it into low Earth Orbit, and drop it on Federation General HQ at Jaburo! Now do you see? They anticipated there would be a war with us, so they built Jaburo under 1,000 meters of bedrock, but this will flatten even that!
Ramba: You want me to do this?
Dozle: I do! Using your mobile suit forces!
Ramba: I refuse!
Dozle: You what?!
Ramba: Now I get it. This is something that Lord Gihren would come up with. But a military man like you should never even suggest such a thing! This is the work of the devil!
Dozle: The devil? Look who’s talking! You have the blood of a hundred million Hatte civilians on your hands! You’re well and truly a devil yourself! Those Hatte guys will be dead either way, so wouldn’t you say that making their deaths count for something is the sensible thing to do here?!
Ramba: I would not!
Dozle: Why the hell not!
Ramba: Admiral Dozle. This war is madness. Zeon Zum Deikun would never have ordered this war. I want no part of it!
— Mobile Suit Gundam: The Origin - Clash at Loum episode 5, English subtitles, 9anime.to version
His principled opposition to war crimes is incompatible with the Zabis’ Zeonism. He believed in Zeon Zum Deikun’s vision of peace, and was demoted for it. He spends the rest of his life in obscurity.
In Mobile Suit Gundam: The Origin, that is. That Ramba still had black hair in 0079.
In the original Mobile Suit Gundam, a grey-haired Ramba Ral is found on Earth, where he is The Blue Giant, a renowned guerrilla warfare expert who is assigned to defeat the Federation ship The White Base. Crowley Hamon still accompanies him.
This version of Ramba Ral is still a man of principle, but he’s less political, and has found success by being a good soldier who follows orders. When he encounters Artesia on board the White Base, he introduces himself as a servant of her father, and does not kill her. It is at this moment that he doubts the orders he had been given. He dies rather than be captured by Federation soldiers.
I would say that both are men of principle, but the grey-haired Ramba drank the “good soldier” juice while the black-haired Ramba drank the juice of his father’s Zeonism. Grey-haired followed orders, but black-haired thought about them.