The term “Precious Topaz”, the finest quality of topaz, is often used to distinguish between true Topaz and lookalikes.
Citrine and Yellow Sapphire have been sold as “Gold, Scotch, or Madeira Topaz.”
Brown Topaz does occur naturally but the term “Smoky Topaz” refers to Smoky Quartz.
Blue Topaz can also be natural but most have been heat-treated to produce the specific trademarked Sky Blue, London Blue, Swiss Blue, etc.