Could it be possible to have a way to test the dyes for free before having to spend like 100 gold to buy them without even knowing what your gear will look like?

Actually yes there is kinda. Talk to the seemtress and talk to her. When you go to the menu to craft the armor you go and click dye color and you see a bunch of colors but, I do find this a cheaty way IC or OOC.

When using the Seamstress for dye, you do not recevie the exact name.

Unless it is an EfU-unique color, you can test it out in toolset. If it is one of the EfU exclusive colors, such as Deep Hound Dye, then I am not sure. Perhaps a color palette or something in the like would be of help?

If you acquire a dye that you are not sure about, you can export your character and test it in a local module. This is also useful when it comes to checking which parts of your clothing will the dye dye and arranging it to your liking without having to spend too much gold.

Szgk, that's a great frickin idea. Why didn't I think of that.... Of course you still have to purchase the dye. A color chart would be nice. Paying 100+ gold for a metal dye when you're a broke fighter is a bit steep if you're just hoping it's a specific color.

Unless I'm mistaken, metal dyes' names are pretty descriptive. Those available in the shop, that is.

Often, the names can be very misleading.

You don't have to buy dye at all. As for the names, some of the Svifneblin "color" dyes are completely false, I tried grey svirf metal paint and it was blue.