You will be tasked with heading toward blueville to meet the king and will enter a section of map with 2 arrows, 1 to blueville and one with a picture of a carrot, take the carrot road and almost immediately you should see a Red who looks an awfully lot like Minecraft Steve and asks you get him a diamond pickaxe.. Remember where he is because you will need to come back to him after you progress this part of the map. There is a colour change station that will require you get a barrel (located above the acid pool and requires you have the jump pads active) to make it work as well as a few pickaxes about the level that you should find as you naturally progress it, most are in houses. You should also see a farmer in and around this area with seeds... You can use a red seed over by the water sprinkler to grow a red flower, if the gun/seed don't seem to do it for you.
Assuming you have the water pump working, and have used your Red gun/red flower to colour the pump water, simply place a pickaxe on the platform and change it to red, bring this all the way back to Red Steve and he will tell you how red stone can't be used to break anything and ask how you managed to craft it. Achievement Unlocked
*Don't stop there, go turn the pickaxe blue using the tree leaves above the colour changer and give it to Red Steve so he opens the door behind him... This is for "Payback achievement".. I'll see you over there.