dataentry

I use Jaspersoft studio to create labels for a grocery store. I want to have a text box on the label that has different background colors that correspond to different vendors. I have gotten as far as creating a conditional style, but I do not know how to code the expression for the conditional style so that when a certain vendor name is the in the text box it triggers the conditional style. I know very little about Java so I am at a loss. Any ideas? Thank you in advance.