For what it's worth, both religious and secular African American "folk songs" have lyrics that follow a pattern of referring to one or more person "dressed in" a certain color.

For example, in some songs, women wearing the color "red" seems to be associated with mourning someone's death {Or perhaps it was a reaffirmation of life since red is the color of blood}.

"John Henry's lil mother,
She was all dressed in red,
She jumped in bed, covered up her head,
Said she didn' know her son was dead,
Lawd, Lawd, didn' know her son was dead"

@displaysong.cfm?SongID=3243

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In other 19th century dance songs, the lyrics referring to a woman being dressed in "red calico" may just be a reflection of the value that was placed on placed on a color other than the drab dark colors that were the norm for African American women who couldn't afford anything else.

"Gwineter take my gal to de country sto;
Gwineter dress her up in red calico".

Thomas W. Talley Negro Folk Rhymes
"I Would Rather Be A Negro Than A Poor Black Man"; Kennikat edition: p.42

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A line in a song/poem entitled "When My Wife Dies" that found in that same 1922 book Negro Folk Rhymes suggests that there was a superstition against wearing the color "black" when a person dies"that appears to be associated with a belief in reincarnation:

"W'en I goes to die, Nobody mus'n' cry,
Mus'n dress in black, fer I mought come back.
But w'en I'se been dead, an' almost forgotten;
You mought think about me an' keep on a-trotten."

{Kennikat Press edition; p.6}

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Here are two verses from a version of the New Orleans Mardi Gras Indian song "Iko Iko" that refer to people wearing certain colors:

Look at my king all dressed in red.
Iko, Iko, unday.
I betcha five dollars he'll kill you dead.
Jockamo fee nané...

See that guy all dressed in green?
Iko, Iko, unday. He's not a man;
He's a lovin' machine.
Jockamo fee nané.

thread.cfm?threadid=23200

These verses mimic the color verses in "Wade In The Water", However, I don't believe that the specific colors have any other significance but to complete the set up the rhyme.

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This verse from the old African American song "Railroad Bill" also follows the familiar pattern started by the "Wade In The Water" color verses of referring to someone "dressed in" a certain color. But in that verse the reference to color is just descriptive of the color uniforms that were worn:

"Well, the policemen all dressed in blue,
Comin down sidewalk two by two,
Wus lookin' fer Railroad Bill."

thread.cfm?threadid=45143

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Also, see this thread thread.cfm?threadid=91064 Songs About Wearing Red for more... um...songs from various cultures about wearing red.