Ye-ye, Blue is! :'> Slightly leaning towards male, but I feel weird calling Blue male right now, ahh. (Only because I've called Blue "she" for the last 7+ years) So I need to just like, slowly go into calling Blue male. XD And who knows, maybe I'll always keep Blue a-gender, only time will tell~~~
But, ahh, I love characters with all different sorts of genders, and sexualities, and all that. ~(o3o)~
Sex is something you are born with. You are born with either male or female parts. Perhaps genetic mutations cause a person to have both or neither in rare cases, I don't know.
Gender is something you identify as. Cisgender is when you identify with the sex you were born with. Such as if you were born with female parts and identify as female. Transgender is when you don't. Such as if you were born with female parts and identify as male. Of course, there is more than just those two, like genderfluid, but they are the most commonly known. Agender is when you don't identify as either male, female, or any other genders there are, I believe.
It's not the best of explanations, but I think it gets the point across.