It's hard to say.
My beard is mostly dark brown, with very little variation,
But the hair that I grow on my head...when it's not dyed, is extremely varied as far as individual strands go,
While most of it's brown, I've got random red running all over the place and a random streak of almost blond hair at the top of my head...
It's not as noticeable as it used to be, I was once known as the male version of Rogue from X-Men...pretty awesome,
But yeah...consensus says that it's normal. No worries.