brown cloth and dye

For most real world pre-industrial Earth societies, and in Scarterra, brown clothes were commonly considered peasant clothes.   Symbolically, brown is color of the dirt. This doesn't mean brown clothes are considered the color of poop. It's not that low status. In an agrarian society, the majority work outside in the dirt and dust, so brown clothes is associated with the common, not the lowly.   The bottom tier of the clothing hierarchy is not brown cloth, it's undyed cloth. Which in the case of linen, cotton, hemp, beige is the natural state of most cloth.     Wool in Scarterra comes in a huge variety of colors, so it is more socially acceptable to wear undyed wool, especially if the wool in question is of one of the so-called rare colors. Very few Scarterran sheep are beige (which is good because such wool would not be worth much), but the plurality of them are brownish if not brown which is considered common though a rich brown wool would be valued above average.  

Brown cloth was not as common as you probably think it was

  It almost goes without saying that television and movies are not accurate portrayals of real world history. Whether it's a fictionalized retelling of historical events or a purely fictional setting that is loosely based on real world events, you are likely to see lots of peasants wearing brown clothes.     This is not historical accurate, but it feels historically accurate because we are so used to seeing things the wrong way. Part of this is a cinematic trick that predates film and goes back to the days of stage. If the extras have clothes that cause them to blend with the background, this makes the protagonists more clearly visible to the audience.   I'm not going to pretend that Scarterra is historically accurate, but in real Earth medieval history, it was not unusual for peasants to wear fairly bright colored clothing, and this applies to Scarterra.   The "Medieval Era" covers roughly 500 years and a huge land mass, so there was a lot of variation. In some times and places, there were laws limiting the number of bright colors commoners could buy in their clothes because some commoners were being mistaken for nobles. There wouldn't be a need to pass these laws if peasants weren't able to buy bright clothing relatively easily.   Medieval art is full of peasants wearing bright and cheerful clothing. Records of inventories and shops back up that tailors regularly sold bright colored clothing to peasants.     So in short, brown cloth is the most common color Scarterran peasants wear but it's far from the only color peasants wear. Once their basic needs are met and they have a little bit of extra money, the first luxury many peasant families buy is often bright colored clothing and once a peasant has a nice outfit, he or she is going to take good care of it to make it last as long as possible.   A lot of peasants made their own clothes, and if fancy dyes are more expensive, they save a lot of money making and dying their own clothes.