So I was messing around, trying to break the solar system with a massive planet, so I spawned a blue gas giant close to the sun. It started becoming a comet, and that's when I realized the planet was only 0.2 Jupiter masses. I started to increase the mass, and I din't see the reason to not turn it into a star. When it did, it was a 0.1 Solar mass blue star. I increase the mass even more, and it became darker and darker shades of blue:
And it kept it's comet tail, even after becoming larger than the sun.
It seems that Gas Giants keep their color when transitioning into stars.
I couldn't experiment with the darkening feature because of the grand finale;
When it collided with the sun, it shrank into three sizes in three frames (Like FPS frames), and then disappeared, letting the sun continue on its merry way.