Solution to: Save your friend

Jack: The crime happened at 3.00 PM and by considering the location of the window and the position of the sun, the sun rays would do a magic.

The sunrays from the window perfectly falls on the prism , by a known phenomenon called dispersion, the color of the light gets scattered. By calculation, I found a person standing outside the window can see red light falling on that screen.

So, when Kayla saw a person with pink shirt in the crime since from the window, the true color of the shirt must have been blue!

red+blue= magenta which looks like pink

Your primary statement of murderer being in pink is broken.
So, though we don't know who the murderer is, we know Steve is innocent!