Hello,
The 2 blue USB ports are USB 3.1 ports and the 2 black USB ports are USB 2.0 ports. The only difference between the 2 colored ports is the transfer rate that data is being sent between your computer and another external device (so basically the blue ports are 10 times faster then the black ports when you want to transfer data over to, for example, a USB external hard drive).
Hope this helps.