I don't claim to be an Egyptologist, but I know I would
have heard such a thing before. Are you perhaps referring to
the Dog Star, Sirius, which was important to the Egyptians
as it marked the flooding of the Nile River.

There are ancient reports of Sirius being referred to as
red in color. Some interpreted this as the distant sun's
companion star, the white dwarf Sirius B, may have been
a red giant at that time. Other scholars now think that
the color intepretation of Sirius was largely symbolic due
to its prominent nature in the night sky (it is the brightest
star after Sol) and its usual closeness to the horizon,
where the star often twinkles in a rainbow of colors.

http://en.wikipedia.org/wiki/Sirius