The blue SATA ports on the EVGA 730i (113-YW-E115-TR) are for AHCI and RAID use only. 

When the SATA Mode is set to IDE, the blue SATA ports are disabled.  By default, the board is set to IDE mode. 

If you are not going to be using AHCI or RAID, it is best to fill up the black ports first, then the red ports.