Objective: How do I prepare the yeast when making indian garlic naan?

Which of the following solutions is more sound in terms of naive physics reasoning?

(a). In a medium bowl combine the yeast, sugar, and water and let sit until foamy (takes about 5-10 minutes)..
(b). In a medium bowl combine the yeast, sugar, and water and let sit until brown (takes about 5-10 minutes)..
(a).