I mean, I want blue because blue has repeatedly been used in this quest as a colour representing good vibes, and because it ties into the idea of Water and rain being givers of life on a desert planet.
I don't recall the specific examples, but blue is generally tied to good in Starwars fics because it is the generic "good" color for the force, not because of anything specific to the color or the story. While blue
could be tied to water in this quest specifically, I don't think it has been, at least not consistently. By the same token, white and silver can also be tied to water, in the form of clouds that give both water and shade, and the way light flashes off water in the sun. Remember, water only really starts to look blue when there are specific minerals present or when you have a lot of it; silver is probably a better connection for someone living in the desert.
Beyond that, silver lightsabers, specifically, are closely tied to Tatoonie, in a way other lightsaber colors aren't. I didn't mention it before, but
Durindfire crystals also have another, potentially interesting connection to Annakin. On Tatooine, they're viewed as worthless by most of the inhabitants, except for Jawas who use them to make protective lens, but they're incredibly valuable to the rest of the galaxy and I suspect the Huts intentionally cultivate this impression, because it gives them easy access to a valuable resource that they can use to bribe the Republic. This is a close parallel to how Anakin was treated as a worthless slave on Tatooine, not because he was worthless, but because it was useful for Depur, and now he's proving his real worth, beyond his slaver's grasp.
On a more mundane note, it might also provide an unique point of connection and discussion with one of the other padawans (unfortunately, I've forgotten their name), since they'd also have experience with those crystals.