Green, blue, red and pink. That is the order of the four colors that you must make the "Brother" touch one time in the room with the mirror to make the stairs to the third floor appear. For those who go up, let me save you time, no, the shovel is useless up there.
Ok, If you already know exactly where you have to be for the brother to step on the corresponding colored tiles, you save me time. The problem why it won't allow you to activate the stairs will be because you are walking towards the tiles instead of jumping towards the tiles. One of the things that is "difficult" about this process is that the brother will activate the tile for each step he takes, therefore, if you walk towards the tile the mere act of stepping on it to enter it would already be activating it, now if you walk out the brother would be activating it again by go out of that tile, causing the process to be ruined. Recommendation? Step on the tile by jumping towards it and get off the tile by jumping, avoid walking on them, remember that we are looking for you to activate them once. Let me know if that was the problem or I'll see if I can upload the process to the page as a gif.