I'm somewhat critical of the colors of this APOD.
The Great Carina Nebula. Image Credit & Copyright: Demison Lopes
The Great Carina Nebula. Credit: Harel Boren
Harel Boren's image is an RGB one, but I don't know what filters were used for today's APOD, although I suspect a red hydrogen alpha filter and a bit of green OIII. The OIII filter (if one has been used) would contribute to the greenish-white tint of the region around Eta Carina and further up along a dark ridge at upper right in the APOD. I can't protest against the greenish tint here, because undoubtedly there is a good amount of green OIII emission here.
What I don't like about the APOD is the fact that the cool red stars are the same shade of red as the hydrogen alpha nebula. That doesn't happen. "Red" stars are some shade of
yellow-orange, but hydrogen alpha is
red-red. It may be lightened to a
pink shade in the presence of hydrogen beta.
Take a look at the star HD 92397 at upper right in both the APOD and in Harel Boren's image. In the APOD it looks like a white star with a brick-red halo. In Harel Boren's image it looks almost all white. Well, the true color of HD 92397 is very similar to the color of Aldebaran. HD 92307 is the same spectral class as Aldebaran, although several times more luminous.
HD 92397 is the same color as Aldebaran, but it is the same color
as the red emission nebula in the APOD.
HD 94096, by contrast, is a brilliant red supergiant whose B-V index is even redder than that of mu Cephei (the "Garnet" star).
But HD 94096 is not as luminous as mu Cephei. The Gaia parallax of mu Cep puts it at a distance of more than 27,000 light-years - far beyond the Carina Nebula! - and coupled with its V brightness of 4.08, gives it a V (yellow-green) luminosity of
1.3 million times that of the Sun! In yellow-green light, from a cool red supergiant star! In infrared (I) light, its magnitude of 0.22 gives it a luminosity of
45 million times the Sun!!!! And a even farther infrared wavelengths, (K), its luminosity is
270,000,000 times the Sun!!!! 
Is this even possible, or is the Gaia parallax wrong?
The Gaia parallax of HD 94096 doesn't make this star
so humongously bright. Even at K wavelengths, it is "no more than" some 700,000 times that of the Sun. Still, it is even more deeply orange in color as Mu Cephei.
As for HD 93070, it may be a long-period variable similar to Mira. I tried to find a good visible-light picture of Mira on the net, but it was hopeless. Mira is "known" for being very red, and for that reason the internet images of Mira have been reddened to a ludicrous hue. Mira's B-V index is modest, around +1, and even its R magnitude is unremarkable. However, it is extremely infrared-bright. At visible (V) wavelengths, it is only 16 times brighter than the Sun! 16 times, can you believe it?
But at K wavelengths, Mira is 50,000 times brighter than the Sun! Can you believe it?
So anyway. All red stars are the same shade of red in today's APOD, but in Harel Boren's RGB image, the red stars come in different shades.
Ann
The Great Carina Nebula
Is this even possible, or is the Gaia parallax wrong?
