For MIX option, you can mix all available colours
For 150 sheets, you can mix up to 3 colours (50 sheets each colour);
For 250 sheets, you can mix up to 5 colours (50 sheets each colour);
for 500 sheets, you can mix up to 10 colours (50 sheets each colour).
And please leave us a note for the colours you after otherwise we will randomly send.