notes red after transposing but within playing range of instrument

Hi, I hope someone can help me!
I added a new instrument (flute) to a piece of music. I then created a new part copying a violin part to create the flute part, and transposed the flute part to an octave higher. However the "A" notes show as red throughout the whole piece, even though it's definitely within the playing range of the flute. It's the A note above middle C. If I copy the notes from the Bb clarinet part the A notes stay black, but with the violin which is in also a C instrument, the A notes show as read. I even tried changing the key signatures from 2 sharps to 1 sharp, and even to flats, but regardless of the key signatures the A notes still appear red. I'm really puzzled. Is there anything I can do to get rid of the red noteheads?