Hair
There's one thing that Leman Russ, Lion El'Johnson and Sanguinius have in common. They have all at some point dyed their hair. This is where the similarities end.
When Sanguinius dyes his hair, it is because he is grieving. It is not a custom from Baal: no one really knows why the Angel considers black hair an inherent part of mourning. Of course, none of his brothers have asked. Each of them has his own little idiosyncrasies, so why bother Sanguinius for his?
Like most of his Space Marines, Leman Russ has grey hair. It's also precisely the reason why he first dyed his hair blonde, then red. With grey hair, he didn't stand out that much and his pride wouldn't let him accept this. As a leader, he had to be recognizable. Changing the colour of his armor was out of question, so he did the next best thing and dyed his hair.
Unlike the previous two, the Lion does not regularly dye his hair. He did it only once and only because it would be inconvenient not to.
There are many types of silence. The one that currently surrounds Lion El'Johnson is usually described as icy. It would have been daunting, had he been a normal human; given that he is a Primarch, it's terrifying.
"Could you be so kind and repeat this?" he asks and the hapless diplomat, who had been explaining the customs of the people they will be negotiating with, wishes the Primarch would just yell.
"Your hair can be seen as an insult by them, sir," he barely manages to say.
"Yes?" the Lion drawls, making the diplomat cower.
"As part of their punishment a coward's hair is dyed blonde there," he continues. "If they have to negotiate with blonde leader, they might jump to conclusions."
The Lion takes a strand of his long hair and inspects it in silence. There's a russet undertone to it, but it is undeniably blond. For different human cultures the same colour can denote various things. In some cultures black is the colour of mourning, in others it is white. Therefore, he knows what he should do and why. There is much more to gain by being pragmatic, then by demonstrating disdain for the other culture.
Still, the sheer nonsense of the situation is getting to him. His hair shouldn't matter in diplomatic relations.
With a sigh, he says, "Give me a few hours. I'll do something about my insulting hair."
AN:
This story has been brought to you by various inconsistencies between the descriptions of Primarchs in BL books and their pictures.
Okay, I admit, the part about Leman Russ actually having grey hair is my idea (or to be even more exact that of my brother's). In canon, he's usually portrayed as red-head, but there's at least one picture where he's blond. So, why grey hair? 'cause Space Wolves' hair turns grey once they matured enough. It makes sense for Leman to share this trait.