<img src="http://ghchart.rshah.org/sigdelsanjog" alt="Sanjog Sigdel's Contribution" />
replace the username sigdelsanjog with your github username and the emphasis text inside alt tag alt
You will then see following output:
You can also add a different color instead of the default green one. And this is how you do it. In your image source link you need to append any HEXCombination colour code to generate chart in different colot that you want