I was wondering if there is any difference between the PWD bridge between a blue board and green board. Is one newer than the other?
Yes. One is blue and one is green. Almost certainly just different production batches. I doubt that there are any functional differences.
J.P.
The green ones have a bit of yellow. They sound warmer.
Yeah, but the blue boards sound really cool. :))
J.P.
Yes, they are better for 1950’s and early 1960’s jazz, and some forms of hip-hop.
The only thing that is good for hip-hop is the trash can, or bit bucket in the digital domain. 
Yes, I know that some people actually think that it is good but it does seem to be one of the more polarizing genres.
It is a bit curious though. some companies make the soldermask color part of their brand or trademark. This may just be a case of using different circuit board manufacturers for different production batches.
J.P.
wingsounds13 said: . . . some companies make the soldermask color part of their brand or trademark.
I was unaware of this. It makes sense though.
Okay, not Trademark ™ but product identy. Still yes, particularly a few (PC) computer parts manufacturers do use soldermask color as part of their brand and product identity. No, I don’t remember who, but one consistently uses red and another blue. If you are familiar with them you can name the brand from without having to read it.
In the case of the Bridge I am sure that it is just from a different production run and possibly a different board house.
J.P.