General Studies · Seating Arrangement / Linear Ordering

Seven different coloured boxes (red, yellow, green, blue, magenta, purple, and orange) are kept one above the other but not necessarily in the same order. There are only four boxes between the yellow box and the blue box. The red box is just below the blue box and just above the purple box. The green box is kept at the botto m-most position. What is the colour of the box that is at the topmost position?