Some of the brown dyes contain potassium permanganate, going purple in water but leaving a brown stain.
I very much prefer the spirit-based dyes. I used to get Wilko own brand (made for them by one if the UK factories) but Blackfriars and Rustins seem the same. Colron sell a "refined" water based one now that is nowhere near as good. I apply by brush for speed.
You can mix them in a jar for colour variation, which looks more natural. They are just combinations of brown, red, yellow and black colours.