The third color in the carvariations sets that effect, it's currently set to 0, which is black. I believe Metallic Silver by default uses 5.
Thank you so much for the reply! So I tried what you suggested and it absolutely is tied to the effect and what I was looking for. But it still wasn't matching so I did some digging into the carcols file and thought it was tied to the MetallicID (EVehicleModelColorMetallic_5) and went through that entire gamut to no avail. Then I used a trainer to save the color I wanted as a preset and looked at the ID array it saved in the settings. Turns out the value I needed for Metallic Silver was 111. Not entirely sure where it pulls from but it works now lol