According to the VW Vanagon FI service manual, yellow is correct for 2.1

a scan of the page is here:
http://www.californiavan.com/Manuals/Digijet/vanagonDigijetP56.pdf

Blue injectors are for AFC systems (air cooled vanagon and late buses with FI)
Yellow (gold?) injectors are for Digijet/Digifant engines (1.9 and 2.1)

>
>Now, it there a difference based on the color? I'm making the assumption
>that Bosch would use distinct colors on such a product only to delineate
>differences.  In addition, in a recent post (or link provided by someone) a
>mention was made referring to the color of the injectors, I believe saying
>'gold' was correct.  Try as I might, I can't find that post or reference,
>but the reference to color was made causally anyway, no details.
>So, can anyone answer the question.  Do the colors mean anything and if so
>what?  And which is correct for the Vanagon 2.1L WBX?