To get the BEST looking FSL though you want to use the same color thread
on both top and bottom.
I know that
ABC Embroidery Designs sells bobbin thread in the same colors
as the top thread, but from ALL the designers, instructors, Retail store (where
machines purchased) said tat using emb. thread on top does not hurt anything.
Even my repair guys use the same thread.
Of course everyone has their own preferences on what they will or will not use.