Read the full text of Henry VI Part 1 Act 2 Scene 4 with a side-by-side translation HERE.
Things do not go well in this scene. Imagine a feud between high school cliques. Then imagine a feud between high school cliques where the members have huge political power and carry swords.
This scene starts off with a quarrel: Richard Plantagenet is having some sort of fight with Somerset. Interestingly, we never find out what the fight was actually about, but it spirals out of control pretty fast. They already had to take it outside, as Suffolk says.
Somerset decides that Warwick should arbitrate. Warwick declines in a tactful and eloquent speech, though, so Richard says he himself is obviously right, as anyone could see.
Somerset says the same. You can almost hear them shouting, "Is not, is too!"
Various people take sides, but the scene really gets interesting when everyone starts plucking roses. Wait, roses? Have we suddenly gone all Hallmark card? Nope.
Here's the deal: Richard Plantagenet's family, known as the House of York, is symbolized by a white rose. The House of Lancaster is symbolized by a red rose. Later, a war will officially start between the two houses over the crown, and this will be the start of the Wars of the Roses, a turbulent period of civil war in English history.
So this scene is ominous. Maybe storm clouds would be more appropriate than roses.
Richard asks his followers to pluck a white rose.
Somerset asks his followers to pluck a red rose.
Warwick now does take sides with Richard, choosing a white rose.
Suffolk sides with Somerset, choosing a red rose.
Vernon's all hold up and points out that they should agree that whoever gets the most roses wins. Somerset and Richard agree.
Final count: Somerset: 1 rose, Richard: 3 roses.
Richard kind of rubs it in.
They keep arguing, and Somerset insults Richard by calling him a "yeoman" (2.4.82), a much lower rank than his family actually holds.
Warwick points out that Richard's grandfather was a Duke, and not only that, but also the third son of a king.
Somerset says basically "So what? Richard's father was executed for treason. Doesn't that disqualify Richard from being a nobleman?" (It's true. You could be kicked out of the aristocracy if your father was convicted of treason.)
Richard says his father may have been executed for treason, but he wasn't actually a traitor. He says he won't forget these insults.
The quarrelers part on bad terms, and Warwick says that Richard will be restored to the aristocracy at the next parliament, where he will be named the Duke of York. Warwick also says he'll keep wearing the white rose as a sign of support for Richard, a bit like wearing a campaign pin during an election.
Warwick makes an ominous prophecy: Today's argument will bring about many deaths. This is a hint at the Wars of the Roses—it's like knowing that galactic war is coming as you watch the first three Star Wars films. However solid the Old Republic seems, you know it's going down.
Richard thanks the other guys who sided with him, and they all head off to dinner. There's a lot of going to dinner in this play. Maybe Shakespeare and Co. were hungry when they wrote it.