What is 221G Blue slip

[tejastrivedi]

some one please help me. What is the difference between blue slip and green slip ?
First time i was received green slip and now I have received blue slip. Details in both slip are same. No other difference except color. I am confuse what to think.

Please help and guide me.

[shervin143]

https://www.immihelp.com/usa-visas/221grefusal/