The closed-caption indicator color represents whether there is a closed-caption error currently or not. Blue indicates the presence of good CC data whereas red indicates the presence of bad CC data or the absence of CC data. What you are most likely seeing is a known issue where the CC data is coming in bursts (as closed caption data usually does) and periodically triggering "CC Missing" errors which turn the text red. This is normal behavior for the WFM700 since technically it considers missing CC data to be an error and CC data regularly goes missing between words and when nobody is talking in the video. You should be able to suppress these errors by disabling the "CC Missing" error in the configuration menu.