The Belts apply to both Six Sigma and Lean Six Sigma (LSS). Here is a PDF explaining the LSS Belt System.

White Belt (standard or for Leaders): Involves one day of training usually provided as general overall knowledge to large groups. It is not project based. This content can also be provided to Leaders with added subjects related to leadership and deployment of the LSS concepts and is called White Belt for Leaders.

Yellow Belt: Consists of two days of training. This is the same as White Belt with additional detail allowing for better application of the concepts. It is not project based. This content can also be provided to Leaders with added subjects related to leadership and deployment of the LSS concepts and is called Yellow Belt for Leaders.

Green Belt: Six days of training are required and are usually spread out over three months. This certification training is based on project application and results. On the job, those trained as Green Belts usually work part-time on projects in conjunction with other responsibilities.

Black Belt: Involves twelve days of training usually spread out over five months. This certification training is based on project application and results. Traditionally those trained as Black Belts worked full-time implementing Process Improvements leading high-impact projects. They train and Mentor LSS Green Belts.

Master Black Belt: The Technical Mentor for Black Belts and Green Belts. The process of becoming a Master Black Belt takes anywhere from one to four years after completing the Black Belt course depending on the candidate’s experience and opportunity to practice Lean Six Sigma. They act as consultants and trainers and stay involved both strategically and tactically with Process Improvements.