It has a tan to brown color from the residual impurities. Some food faddists attribute beneficial results from using this but unless a lot is consumed, the potential benefits are very low. Demerara is usually a dark brown shade while turbinado is lighter, more of a tan or taupe color. This is the residue of the sugar after the crystalized portion has been removed. The choice of names for this sugar syrup seem to reflect regional language preferences rather than any major differences.
Regular treacle is an inverted sugar produced from the residue of refinement.
The acid treatment darkens it. Molasses is filtered and may have a sulfur compound added to sterilize and stabilize it. Find one company's product you like since that may be the only level of consistency obtainable. Like molasses, this is a syrup that remains after the crystallizable sugars have been removed. However, since the syrup is removed later in the refinement process, it does not have as heavy a taste or color as molasses.