I've read that there will be a dye preview window in Book 14, which will be a godsend.

Evil scholars like Malduster price their dyes so exorbitantly high that testing dyes on a particular piece of clothing/armour was always a costly hit or miss affair. Nothing like wasting expensive dye on an item and seein no discernible difference from its default color!

Hah yeah! Finally it seems! They listened to you