Because though the sun emits strongest in the green part of the spectrum, it also emits strongly in all the visible colors – red through blue (400nm to 600nm). Our eyes which have three color cone cell receptors, report to the brain that each color receptor is completely saturated with significant colors being received at all visible wavelengths. Our brains then integrate these signals into a perceived white color.
If that was the case, wouldn't the moon appear more green?
I guess the difference in colors is not as strong as in other artificial light sources. So it wouldn't be entirely blue, just "blueish than it seems". When measuring how true are colors under a certain light, a common measure is the CRI or color rendering index. The sun is taken as a 100CRI or perfect score reference. So maybe the article is a bit misleading
I like the article's title much better - "What Color Is the Sun?" because, as the article says, there is no simple answer.
And color, anyway, at least in the way most people mean, isn't an absolute property of objects, but a changing mix of the properties of what produces the light, what reflects the light, any intervening medium that might scatter or absorb the light between the emitter and the reflector, then also the way our eyes perceive light (in a very limited visible range, with variable sensitivity depending on brightness and the cells in our retina) and the way our brains interpret it.
And even the way our languages divvy the smooth visible spectrum up into discrete color blocks (e.g. we arbitrarily agree where the cutoff is between blue and green, but that's socially constructed and differs between cultures.)
Just look at the "are tennis balls green or yellow" and "is this dress blue and silver or white and gold" arguments.
Anyway, though. I enjoyed reading the article! Thanks for posting 👍