Guinness was originally known for light colored ales, not dark stout.
Answer: True.
Brewer Arthur Guinness began making light-colored ales at his brewery when he first set up shop in Dublin, Ireland, in the late 1750s. However, so much porter and stout (a stronger, or "stouter" version of the beer that was popular with street and river porters) were being shipped from London to Ireland, that Guinness decided to create his own version of the style. In 1821, precise instructions for brewing the darker beer were recorded—the beginning of today's Guinness Original and Guinness Extra Stout.