What are the different ranks in Tae Kwon Do?

Depends completely on the school. In ATA schools the ranks are:

• White
• Orange
• Yellow
• Camo
• Green
• Purple
• Blue Recommended
• Blue Desided
• Brown Recommended
• Brown Desided
• Red Recommended
• Red desided
• Black Belt (Red-Black Black Belt or Black Recommended)
• 1st Degree Black belt

But once again it depends entirely on the school, see related links below.