Flann

The Old Irish form is Fland.
In modern Irish, Flann is pronounced in three different ways according to the three main dialects:
Gaedhlig Uladh [Ulster Irish, northern] has /fˠl̻ˠan̻ˠ/ kind of like English "flan";
Gaeilge Chonnacht [Connaught Irish, western] has /fˠl̻ˠaːn̻ˠ/ like English "lawn" with an f before it;
Gaelainn na Mumhan [Munster Irish, southern] has /fˠl̻ˠaun̻ˠ/ like English "clown" if it began with an f.

Flann is a Gaelic expression which means "ruddy complected."

Flann doesn't mean red in Irish Gaelic. Red in Irish Gaelic is dearg.