At the beginning of the movie, Legolas says:"A red sun rises. Blood has been spilled that night" (or at least something similar).
And in Helms Deep King Theoden says" for a red dawn". Then he (and the others) ride out, the sun is rising, but it isn't red! There has been so much blood spilled that night, why isn't the sun red? I mean Theoden had just talked about it, did PJ forget? Or did he want the sun not to be red??