The yellow box flag (which confusingly has words "red flag" in it but I digress) is shown immediately, only needs one supporter (or rather more supporters than opponents).
The red box flag needs 3 more supporters than opponents.
Edit: DarkStar_ made it disappear.
Maybe you were wrong, both newsilike and SafeDice have enough supports for Active Scam Flag, but their Flag Boxes have different colors. It seems that the assumption of QuickSeller is right.
The Yellow is for when someone is showing "red flags" of being a scammer while the Red box is when the person actually scammed someone.
What is difference between
newsilike (Yellow Flag Box) and
SafeDice (Red Flag Box)

They both get active flags, but one is in yellow flag, and another one is in red flag.
Their profile pages look different too:
Let me guess:
Yellow is for active flags.
Red: is for trust.
So, if someone got both red trust and active flag, their flag boxes will be displayed in Red.
Furthermore, Trust Warning is prioritised than flag:
If someone only get active flag: profile page will be shown with #, like newsilike.

But if someone get both red trust, and active flag: profile page will be shown with Trust Warning, there is no #, like SafeDice.

Lastly, what doest the meaning of smaller font size and grey color of supporters?
