Why are 2x4 bricks hard to get in certain colors? I'm new to the Lego community, so apologies if this is a dumb question.
I am trying to understand how best to get hold of 2x4 bricks in a variety of colors in the brown and green spectrum but am a bit confused as to why they're apparently hard to get hold of at a reasonable price. I already have some from some Classic sets I picked up, but only a few from each. I'm just looking to scale up significantly on how many of these blocks I own so that I can build something large with them.
Pick a Brick doesn't even show brown and dark brown as options, for example. Meanwhile, BrickLink has only a handful of dark brown bricks available at rather expensive prices.
I (naively?) thought that 2x4 bricks would be some of the easiest to get hold of, regardless of the color.
What am I missing here? Is there a genuine shortage of these bricks? Is there a better way for me to get my hands on them?
Prices of bricks are determined by supply and demand, in your specific case, it is the supply side to blame. Check this site which shows how many sets was a particular colour of 2x4 brick contained in, and you'll see that there is no mention of the Dark Brown colour you are after. This means all such bricks for sale come from other sources than opened official LEGO sets that were parted out and sold by pieces, like designer bricks, not officially released sets and the like.
Brown bricks were found in 27 sets, but if you compare that number with the 650 sets for yellow ones, you'll see how it causes the difference in their prices (12 cents vs 53 for new ones sold in average in the last 6 months).
You haven't mentioned a concrete shade of green, but the numbers are similar in that area as well, except for the regular green: Olive Green (3), Dark Green (50), Green (309), Sand Green (18).
The rarity of these shades are best explained by the official LEGO policy of refusing to produce sets depicting realistic military equipment from the contemporary era: see for more here.