They used photoshop. You make any color you want. And they did.
There should still be a way to get the best guess possible that follows some physics.We can see the disk spiral into the core over billions and billions of years using artistic programs. If that gets the point across so be it, if you have to make water run uphill for your theory to be accepted then the search for a reasonable answer is far from over. That doesn't mean we can't come pretty close.
My artistic rendering for a 'black-hole' at the center of our galaxy could be caused by a number of things.
Matter is still giving off light but it's speed away from us is greater than the speed of light so it becomes invisible in an illusionsary way. If matter can move at that speed away from us at that rate then would it also be possible that w wayward star could have been ejected from it's stable orbit and became a 'wandering star'. Should that path bring it to our solar system at a rate that is just below light speed would it's appearance in the sky make it appear that it is moving at a rate that artificially accelerated . In school this would have been a question about train a leaving the station,etc,etc. This would add the element that on this train is a person who is moving in the direction the train is going at a 'rate that is variable' or moving in the opposite direction the train is going which would be slowing things down, somewhat.
If eternal expansion is the fate of the universe then at some point stars will no longer be formed. If starts are looked as a 'heat' the the temperature of the universe would be viewed as getting colder. Any mass that gets colder shrinks in total volume which would mean the speed of our expansion should slow down from that factor rather gravity between atomic particles sized bit of mass being the factor driving universal forces,such as expansion and contraction. If the number of stars was known that could be used to give the current temperature of the universe.The changes that take place after that should see the number of stars being formed compared to the number of stars that die increasing when the universe is expanding and when fewer new stars are formed compared to the number that shed heat the expansion should go into a contraction.
Rules that apply on earth should also apply to the universe. The expanding earth theory needs something to be causing the temperature changes to the molten parts of the earth that is heating it up in general and the signs of the earth getting hotter is the volcanoes and oceanic rifts expanding. At some point the earth will be able to shed as much heat as is being generated so the volcanoes and rifts should become stable and the changes may or may not help mankind.
As the core cools even more it will begin to shrink and the volcanoes will now become sinkholes and the oceanic rifts will become sub-duction zones where the crust is pulled down to the point it breaks and goes into a vertical piece of land rather than a horizontal one. The million year timeline doesn't make it an issue that has to be solved today.
Galaxies are in strings that are all supposed to going away from each other. (that would seem to make collisions impossible yet.. . . . NASA does it all the time) They are visible and that would mean they are 'hot'. If they are getting hotter and the universe acts like a single mass the space between the smallest parts increases as it adjusts for that change in temperature.