Thats... pretty red...
I'm not sure that the colour of the flat matters, as when its stacked and a master flat is created, its a greyscale image...
What type of light box did you make? and what light source did you use?
Other than that, the flat looks ok..
Essentially you want to aim at having the histogram peaking at between 1/3 and 1/2 of the way from the left, and make sure neither the black or white end is clipped...
I would be addressing the colour of the flat though...