This achievement is for Beating the 3rd Puzzle as the Explorer.
You will see the room filling up with water. You must describe the sign above the door to your partner. Tell them what it says and what color it is. They need to spin the valves that match those colors. Once both valves are pinned successfully. You will pop the Achievement and complete the puzzle!
*Idk if the creator is colorblind or what. But the colors don't match. So just pick the valve that looks nearest to that color.
Here is the Explorer Walkthrough: