I have found some different sites of different paint companies.  The links are below.  Give them a look.  You will find them all very interesting and helpful.

 

Valspar: http://www.valsparpaint.com/en/how-to/interior/index.html#/getting-started

 

Kelly Moore: http://www.kellymoore.com/

 

Benjamin Moore: http://www.benjaminmoore.com/

 

Sherwin Williams: http://www.sherwin-williams.com/