How does breath investiture work in combination with colors from gems?

[DarkJester]

Ok. In Warbreaker, when they use Breath to invest in something it drains colors. In the Stormlight Archives, when they use soulcasters, the color of the gem affects how the soul casting works. I could be wrong, but I think I saw once where there were WoB that said it was the color of the gem that affected the soul casting anyway... Soooo... We have people running around on Roshar holding Breath. I don't remember ever reading about the color being drained from a gem in Warbreaker, (keep in mind, it's been a while, so I might be wrong about that.) only stuff like cloth and such. I guess my question is this. If the color of the gem affects soul casting, would the color drained from a gem affect the way Breath worked when investing it. Also, let me go one step farther and say hypothetically said gem was infused with Stormlight. Should that affect it in a different way, or perhaps to a greater extent?

[thekingofpillowland he/him]

I can't be bothered to scour the net for the quote im looking for, so im not 100% on this, but I certain that there was a WoB saying that a using a gem that was not the right colour for soulcasting would basically be like using a bad alloy in Mistborn. So trying to use a discoloured gem could be dangerous, unpredictable, or innefficient. Or it wouldn't work at all. I suspect that trying this with an infused gem would likely make no difference, save for making it harder to drain the colour from the gem, because of WoB saying that invested objects are harder to effect with magic. (For example, hemalurgic spikes and metalminds are somewhat harder to steelpush than regular metal.)

[Spoolofwhool]

Quote

So, in a long winded answer, a gemstone with an impure color would be considered like a bad alloy in the Mistborn magic—it either wouldn't work at all, or would work very poorly. The chemical and color signature needs to be of a specific variety to provide the proper key to accessing the power of transformation.

[source]

No colour would probably result in it not working at all.

[Yezrien]

The color in a gemstone actually comes from metallic impurities, so the Allomancy connection might be more than just an analogy. Soulcasting probably has a lot more in common with Scadrian magic than Nalthian magic.