Well! Um, just to clarify or muddy a few issues, "scarlet" is a dangerous word because in the 18th century when many of our translations were done, it simply meant "bright". So, NO, Caesar is not known to have worn a red cloak, the Latin simply says it was brightly colored. "Scarlet" is a bad translation. It was indeed distinctive enough in some way that his men recognized him at a distance--that was an effect, not necessarily a deliberate purpose. So be careful with translations of colors, they could be wildly inaccurate. Things like this are particularly rife in Bible translations, so it is always best to go to the original language and pick it apart carefully. And then find some good studies on culture, etc., because it may just be that "scarlet" was not considered a fashionable color for *women in Babylon*. Nothing necessarily to do with Rome at all.
Kermes red was an expensive dye, much purer and brighter than madder. Madder was cheap, and made more of a yellowish or orangey red. (It's the same dye used for British soldiers' coats in the 18th and 19th centuries.) Now, just what the Romans or any modern scholars might define as "scarlet" or "crimson" or any other shade is a matter of huge debate, not easily solved. And while colors *did* have significance in some contexts, sometimes they were just colors.
Matthew