>> I consider the colormap choice to be completely arbitrary though
> Arguing about colormap choice seems very strange to be – this is such a common practice in astronomy (and other fields!).
Let's see if I can give a feel for why "physically accurate" and "arbitrary color", when applied to a physical object, seems a problematic juxtaposition. Especially in outreach. Even in astronomy, whose relation with color is... notably flexible. Especially when the colors "arbitrarily" chosen, seem instead optimized for breeding misconceptions. Consider the Sun.
A solar observatory outreach center had a big Sun ball a few meters across. They painted it yellow. When asked why yellow, they explained "It's what people expect".
For years I'd ask first-tier astronomy graduate students (something like): "A five-year old comes up to you says 'I'm told the Sun is a big hot ball! Awesome, I love balls. What color is the ball?' How do you answer the five-year old?". Most said yellow. Of the few who got it right, about half had learned it in a class covering common misconceptions in astronomy education. A follow-up question of "What color is sunlight?" gets most to a "Wait, that doesn't make sense, does it?" moment. Two incompatible memorized factoids, that have managed to remain unintegrated since kindergarten or so.
All fields face challenges of information representation, especially in outreach. But astronomy... is special. Imagine zoology presenting elephants as green, from kindergarten through undergraduate, in education and outreach. PBS and zoos colorize their elephants green, with DaVinci and spray paint respectively, because it's what people expect. A kindergarten student thus misled, only years later might hear "gray", if they become a zoology graduate student, and take a "we suck at teaching" elective seminar, offered at their first-tier center for zoology research, because it just happens to also be a first-tier center for zoology education research.
The closest similar case I can think of in other fields, is video representations of molecular biology. Where a tormented kinesin mouse, desperately clinging to a microtubule wire in a hellish hurricane, with a flailing blur of a vacuole balloon tied to it's tail... somehow gets represented as a lumbering donkey, dragging a massive canal barge, on a quiet summer day. Later revised by making the donkey and barge jiggle in place, for an extra slathering of misleading bogosity. With authors explicitly saying they prioritized "pretty" over fueling misconceptions.
Other highlights include the 2002 "Universe is green" front-page news - outreach outside of their focus, using open-source color software with a bug, and not managing an integrated understanding's "wait, that's not plausible".
Perhaps the app's black background might be changed to green? Given that it's an arbitrarily-chosen colormap, but physically accurate visualization, of a physical object. Or perhaps a nice Scottish tartan, or pink pokadots, for the accretion disk? Both would mitigate the educationally problematic juxtaposition of "accurate" and arbitrary color, by emphasizing the aphysicality of that arbitrary. Actually not kidding (much). When an aphysical representation choice is needed, one can do worse than to optimize for fewer misconceptions, no? Better a tartan Sun than a yellow one?