Why Was Winston Wearing Red Pajamas?

"Ghostbusters II" is one of the greatest motion pictures ever made during the course of human history, but after you've seen it eighteen hundred times you begin to notice certain things. One of those things is the relationship dynamic between the Ghostbusters, specifically the subtle division between the original Ghostbusters and the last man they hired, Winston Zeddemore.

When Ray and Egon are developing the photos of Vigo they all took at the museum they're discussing what type of food to get for dinner that night. Then the photos self-immolate and the door locks shut on them leading Winston to bust in from wherever the hell he was with a fire extinguisher to save the day. I guess it was good that Winston wasn't hanging out with Egon and Ray, but what the hell is that about? I mean they're just going to make the decision to get Chicago Deep Dish pizza without consulting Winston at all?

Winston didn't even get to be on the album cover.

Later on Ray, Egon, and Winston are in the subway tunnel when a ghost train comes screaming through. Ray and Egon jump out of the way and let Winston get fully violated by the apparition. After that Winston is told to measure the depth of the river of slime. Why this has to be done is beyond me... Ray knows the liquid is alive at this point, so why wouldn't it pull Winston in? Fortunately they care enough about Ernie Hudson to jump in after him. When they escape the subway tunnels Egon suggests they all strip naked and there it's revealed that Winston for some reason is the only one wearing all red pajamas while Egon and Ray have traditional grey Ghostbusters pajamas. Why was Winston wearing red pajamas? Why was this decision made? What is the significance, if any? Is it merely a random decision? I don't believe so.