*Copied from my post on the decal forums 2 years ago*
This is how I do it, there may be a better way...
Go to the wiki page for the armor type i want to get the list of colors. ex: http://ac.wikkii.net/wiki/Covenant_Armor
You'll see towards the bottom of the page the colors are all listed, what you want is the ACID. This is in dec, and has to be converted to hex for use in vtclassic looter.
Take the ACID of the color you want, and plug it in to a dec/hex calculator.
Create a rule, and use Slot Exact Palette from the drop down menu
Palette entry # refers to the color "slot" you are going for, ex: veins on celdon sleeves, shoulderpads on amuli, etc
you will have to figure out the slots for each type of armor you're working with, I don't think there is any list out there.
Palette ID is where you plug in your hex
In your example you'd use the 13E8 as your hex code.