Two ladies?

Hi all!

I am a new owner of two beautiful little 6 month old budgies, Johnny (blue) and Cash (gray). They have brightened my life in so many ways. Its all most addicting watching them play, chirp, fly, and devour their chop lol. Originally, i thought they were both males, but Cash’s cere turned brown so i took precautions to prevent little eggs from popping up in the future. But Johnny’s is still light blue and now i am somewhat unsure. I am assuming that Johnny is a male but after reading online maybe he is actually a she? There was a few articles that advised against caging two females, granted they play fight but is that something that might become more serious as they mature?

Any advice is welcomed! =]