* You need an image editor , whit the feature to add colours keeping the texture
I'm using adobe photoshop 6.0 ( i know its old , but its OK for me

)
* A texture ( a full white jersey ) and then modify it ...
like this :
* Fshx ( to import the jersey to the game )
More info :
http://www.nbaliveforums.com/ftopic32814.php ( Cable's Tutorial )
Good Luck with your jerseys !!