First of all, you have to name your labels in a 'scripting' way: My1Label, My2Label, etc... Then, it's pretty simple to do things like:

*Script Bang !AllLabelsSetFontColor
*Script Exec !VarSet tmp 1
*Script Label LabelNext
*Script Exec !My%{tmp}LabelSetFontColor FFFFFF
*Script Exec !VarAdd tmp 1
*Script GotoIf ("%{tmp}"