Well, as Rick James said, what my eye percieves to be as one colour, you percieve to be another. It doesn't matter because blue is blue is blue, even if you see it as what I see as red.
By stating the sky is red without proof you have merely made yourself appear to be more of an idiot.
These FE'ers actually try to present valid reasons for the existance of a flat earth. With Logical thoughtout arguements that make for great discussion. You haven't done any of that.
However, I will oblige you. Okay, the colour we think of as 'blue' is actually the colour 'red.' What does it matter what we call it, as long as it is understood that 'this is the colour of the sky.'