c# datagridview combobox column dropdown list remove elements

Hello. I created a datagridview in visual studio 2013 professional - winfowms. In this datagridview i create a combobox column, which take data from my DB. Its work correctly, but now i want delete data from droplist in this combobox, but not from database. For example: i click on cell and have a list of some elements: yellow, green and brown. I choose brown, and when i click on new row, there should be only: yellow and green. So user shouldn't have a chance to create the same rows.