Obviously it relates to what thisismyknick refers to in #11, and in the novel it's linked to the psychedelic jacket described only a couple of paragraphs earlier.
The musical contains a song actually called "Joseph's Coat".
The lyrics include the following:
Jacob wanted to show the world he loved his son
To make it clear that Joseph was the special one
So Jacob bought his son a coat
A multi-coloured coat to wear
[...]
And when Joseph tried it on
He knew his sheepskin days were gone
Such a dazzling coat of many colours
How he loved his coat of many colours
In a class above the rest
It even went well with his vest
Such a stunning coat of many colours
How he loved his coat of many colours
It was red and yellow and green and
Brown and blue
Joseph's brothers weren't
Too pleased with what they saw
We have never liked him
All that much before
And now this coat
Has got our goat
We feel life is unfair
And when Joseph graced the scene
His brothers turned a shade of green
His astounding clothing took the biscuit
Quite the smoothest person in the district
I look handsome, I look smart
I am a walking work of art
Such a dazzling coat of many colours
How I love my coat of many colours
It was red and yellow and green and brown
And scarlet and black and ochre and peach
And ruby and olive and violet and fawn
And lilac and gold and chocolate and mauve
And cream and crimson and silver and rose
And azure and lemon and russet and grey
And purple and white and pink and orange
And red and yellow and green and brown and
Scarlet and black and ochre and peach
And ruby and olive and violet and fawn
And lilac and gold and chocolate and mauve
And cream and crimson and silver and rose
And azure and lemon and russet and grey
And purple and white and pink and orange
And blue
https://www.allmusicals.com/lyrics/josephandt...
I think performances of it can be heard on Youtube.