Specifically for storage stacking; people can have crazy resource pools mid and late game, even with other storage mods present.

And I personally want the upgrade card to fulfil the same kind of role as 1.20's trim system, with red, blue, green, white, purple, and maybe black and/or orange if they can stand out versus a blank card.

I am not really following. Are you suggesting stack upgrades with higher multipliers? And do you realize you can put multiple stack upgrades in which all multiply the stack size so you can get to insanely high numbers? (e.g. 2 tier 4 stack upgrades multiply the stack size by 16 * 16 = 256, 3 of them by 4096 and so on)

I understand that you can have multiple stacks, but that relies on the upgrade level of the chests. Also, I was referring to the storage upgrade units rather than the cards. Though both of them can benefit from an more extensive levels, with varying use cases for different sets of upgrades.

Now that I am thinking about it...
Given the context of the material grades and rarity, I feel that these new colours would be side-grades. Here are some examples I can toss out:

netherite (black) = 32x (2048)

copper (orange) = 2.5x (160)
emerald (green) = 5x (320)
quartz (white) = 10x (640)
amethyst (violet) = 20x (1280)

ahh right more stack upgrades, yeah I was thinking of adding netherite anyway and had thoughts on copper as well. so I will leave this ticket around and likely implement at least part of these

Would it make sense for copper to be before Iron tier, both in stack upgrade and block upgrade? And in that case, does it mean that the other tiers get a 2X upgrade in the stack?