Search for a string in Data Merge, then change the font color

I'm working on a postcard-style invitation with the addresses on the back. So far, I've finished the invitation and the mail-side template with a Data Merge to a CSV file successfully. Now, as part of my design, I want all of the letter "b"s on the mail-side template (Data Merge) to be yellow. Using JavaScript is this possilbe? This is what I have so far, but something is wrong:

     app.findTextPrefences = NothingEnum.NOTHING as FindTextPreference;

     app.changeTextPrefences = NothingEnum.NOTHING as ChangeTextPreference;

     var myColor:Color = myDocument.colors.add();

     myColor.model = ColorModel.PROCESS;

     myColor.space = ColorSpace.CMYK;

     myColor.colorValue = [0, 0, 100, 16];

     app.findChangeTextOptions.caseSensitive = false;

     app.findChangeTextOptions.includeFootnotes = false;

     app.findChangeTextOptions.includeHiddenLayers = false;

     app.findChangeTextOptions.includeLockedLayersForFind = false;

     app.findChangeTextOptions.includeLockedStoriesForFind = false;

     app.findChangeTextOptions.includeMasterPages = false;

     app.findChangeTextOptions.wholeWord = false;

     app.findTextPrefences.findWhat = "b";

     app.changeTextPrefences.fillColor = myColor;

     app.findTextPrefences = NothingEnum.NOTHING as FindTextPreference;

     app.changeTextPrefences = NothingEnum.NOTHING as ChangeTextPreference;