Arduino uno and rc522 module.

Today i receive a new arduino uno and a rc522 RFID module. I installed the arduino on my PC with windows7 then I have cabled the seven wire of rc522 to arduino. I have installed the library but the rc522 don't work, don't recognize any card. The led on rc522 is red but in every video I found on YouTube is green. The cable is correct...what is wrong? Anyone can help me? Thanks and scuse me for my English.