It's not something I've ever ever really cared or worried about but as it has been brought up recently, I have just re-done these so this is for everyone's information:
I have done away with the group 'Member'
1 post is called FJ Newbie = 1 default star & Grey colour username
50 posts is FJ Beginner = a light green star & colour
125 posts is FJ Junior = 1 seafoam star & green colour
250 posts is FJ Regular = 2 purple stars @ purple colour
500 posts is FJ Senior = 2 Teal stars & brown colour
1000 posts is Loves FJ = 3 magenta stars & purple colour
2500 posts is Adores FJ = 3 blue stars & blue colour
5000 posts is FJ Pro = 4 orange stars & orange colour
7500 posts is FJ Star = 4 dark blue stars & dark blue colourr
10,000 posts is FJ Legend = 5 red stars & red colour
Now you know what each goal is per your post counts etc