Instead of using dynamic colors of in addition to it, you can show correction feedback in text. Next applet shows a green text [b]Correct![/b] when the given answer is correct an a red text [b]Try again![/b] when it isn't.[br]See in next applet how it works and try adding these texts following the Construction Steps.

[table][tr][td]1[/td][td][icon]/images/ggb/toolbar/mode_text.png[/icon][/td][td]Select the Text Tool and create a text [b]Correct[/b]. Color it green.[br]Define the condition to show as [b]ans = sol[/b].[/td][/tr][tr][td]2[/td][td][icon]/images/ggb/toolbar/mode_text.png[/icon][/td][td]Select the Text Tool and create a text [b]Try again[/b]. Color it red.[br]Make it appear if [b]the Input Box isn't empty and ans isn't equal to sol[/b]:[/td][/tr][/table]