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Are you referring to narrowband Ha (which is the red parts of the spectrum), or Hb (which is sometimes referred to as HII is in the blue area). If Ha there are many images that show Ha areas in Andromeda, just Google " Andromeda in Ha " and there they are. Ha is a primary component of ionized hydrogen from emission nebula, whereas Hb is a product of short-lived Blue stars that ionise gas clouds with ultraviolet light. Hb is far less common even in the Milky Way.
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