One explanation for the number of traditional African American songs about religious people dressed in red {such as "whose that yonder dressed in red/must be the people that Moses led"} is the association of West African deities with colors.

See this online passage:

"Shango
by Micha F. Lindemans
The god of thunder and the ancestor of the Yoruba people of Nigeria. He is the son of Yemaja the mother goddess and protector of birth. Shango (Xango) has three wives: Oya, who stole Shango's secrets of magic; Oschun, the river goddess who is Shango's favorite because of her culinary abilities; and Oba, who tried to win his love by offering her ear for him to eat. He sent her away in anger and she became the river Oba, which is very turbulent where it meets the river Oschun.
Shango is portrayed with a double axe on his head (the symbol of thunder), with six eyes and sometimes with three heads. His symbolic animal is the ram, and his favorite colors are red and white, which are regarded as being holy. In Brazil, Shango is worshipped as a thunder and weather god by the Umbandists. In Santeria, Shango (Chango) is the equivalent of the Catholic saint St. Barbara.

Shango was once the fourth king of Yoruba, immortalized after death."

Source: http://www.pantheon.org/articles/s/shango.html

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Eventually, "red" became a color of the lush life, partying, easy women, "red light district" houses of prostitution. Maybe this is a secular extension of "red" being associated with blood and blood being associated with life & vitality.

As an example of the use of a woman wearing a red dress to go out partying, I've always taken a fancy to this song {credited to Johnny Hallyday on this website: http://www.frmusique.ru/texts/h/hallyday_johnny/hiheelsneakers.htm

[But Hallyday wasn't who recorded this song, was he?]


Put on your red dress baby
Cause we're going out tonight
Put on your red dress baby
Cause we're going out tonight
Better wear some boxing gloves baby
In case some fool might wanna fight

Put on your hi-heel sneakers baby
Wear your wig hat on your head
Put on your hi-heel sneakers baby
Wear your wig hat on your head
Well I'm pretty sure now baby
But I know you gonna knock him dead

Put on your red dress baby
Cause we're going out tonight
Put on your red dress baby
Cause we're going out tonight
Better wear some boxing gloves baby
In case some fool might wanna fight

Put on your hi-heel sneakers baby
Cause we're going out tonight
Put on your hi-heel sneakers baby
Cause we're going out tonight
Well I'm pretty sure now baby
But I know you gonna knock him dead

-snip-

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In the 1950s, middle class African American people were generally socialized to not draw any public attention to themselves. That included not wearing "loud" clothes, especially clothes that were red. Red was certainly not a color men would even think about wearing-unless the man was a pimp..And a woman who wore a red dress was labeled "fast".

Those days are largely gone now. I'm not even sure that most Black people [middle class or otherwise] would describe the color "red" as being "loud". And I certainly don't think we would consider it to be "evil."   

I believe that many African Americans associate the color "red" with the Crips gang, and with Valentine's day, and with Christmas {red and green} and with the African American flag {red, black, and green}. Coming full circle, the meaning of red in that flag is [the] blood [of our ancestors].