Yellow, Green, Black belt are different level of training in Six Sigma.
Yellow Belt - course is preferable for Fresh graduates or experienced but who has less experience quality
Green Belt - course is preferable who is having good exposure in quality
Black Belt - managers & above or who has rich experince in quality.
Price will vary in the market depends on the reputation of training institute which you prefer.
If you could provide your contact details your location I may suggest few training institutes.
Lean is not much different method Six sigma
Six Sigma - Problem oriented study methodolgy based on maths & stats
Lean Six Sigma - Process oriented methodology can give solutions before the problem arise.
From India , Madras
Further more, the actual utilization and value of six sigma certification is only if you are doing it through an organization, i mean lets assume that you are working with one MNC and they send you on a lean program now once you are done with the training your organizations lean expert will assign you a project and usually the certification is awarded once you are done with your project and have produced some outcomes. Other wise doing it from some xyz institute or expert will not add substantial value.
To keep things simple i have just attached few of the documents that i have, if you need any thing else let me know.
Asst. Manager Insourcing
From Pakistan , Islamabad