Is there some history associated with this color combo or is it just a random thing? It's not ultraman is it? and there are more...
It's kind of apples and oranges, since they are not all the same. Smogun might be based on the header card color of the IKB Smogon. Gamerudon is definitely based on the colors of the original Yonezawa toys. I've always thought Bullmask reminded me of the Bullmark Minya. Maybe it was simply using the colors from the red Finkshit. Don't really see the Popy Baragon comparison. Chicken Fever and Bigaro, I don't know.
I think it goes farther back...not sure how old that Baragon is but Bullmark was using that combo on Godzilla, Baragon, and some others as well. Here's a Bullmark Minya (1969-ish)
I think it is just a common thought that those colours just look really good together. I have seen it everywhere even beyond Kaiju.
May not the oldest... but making me happy every day Popy late 1970s Vintage Bottle Cap Combattler V Figure Vinyl Chōdenji Robo Combattler V (超電磁ロボ コン・バトラーV, Chōdenji Robo Konbatorā Bui) http://www.auxpeer.com +++ http://www.v-kingz.com (new SMOGUN RED & BAKOBAS GID available for pre-order!)
Bullmarks came in around 1966 so if there is anything older than that and made use of those colors, someone else would know. I don't think they are referencing specific characters...more like one company.
Damn that's a beautiful photo of an awesome Baragon! But, that figure (made by Bear Model BTW) is red vinyl with black spray. This is sometimes called a "Popy" color scheme. Slack was asking about a red base with metallic blue and silver sprays. Not sure about the first figure to have this scheme, but I know there are quite a few vintage figures with this look. Maybe one of the vintage gurus will chime in.
I've never gotten a definitive answer for the "origin" of this color theme (but then, I haven't pestered Flynn about it yet) but it's one of my all-time favorites. I'd buy toys I wasn't otherwise into for this scheme or variations on it. The Blobpus "sunglow" set was a nice example of a contemporary application.
Maybe it's not so much a reading comprehension problem as the fact that those who seem to know something aren't saying anything definitively?