Red is a seller's market (few houses in the inventory, fewer choices for buyers, more comptetition facing buyers, multiple offers possible, sellers not forced to make concessions), Green a market favoring buyers (inventory larger and homes on market for extended time, seller's get edgy, can't move home, inclinded to concessions, price reductions) and Yellow  (yellow) is a neutral market not favoring buyer or seller.

Note, in the upper price brackets we actually see a Yellow or balanced market.

This chart allows buyers and sellers to see the trend in the market not just month by month, but week by week, this one ending on April 23rd.

These charts and this data, pulled from the Northwest Multiple Listing Service helps inform sellers about whether they're priced right and buyers if they can afford homes in areas where they are interested in locating.