Change color of text field when checkbox is selected

[kylem45598253]

I'm created a form where users have a list of check boxes they can choose from. I want a text field to change colors according to which checkbox they select. I have worked through a few ways of doing this, and can make a check box change colors, but when I click off of said checkbox, it goes back to white (or blue as it appears to indicate it's a selectable field) and doesn't remain the color I need it to. 

The code I've tried is: 

event.target.fillColor = (color.equal(color.transparent, event.target.fillColor)) ? color.red : color.transparent;

Is there a way to make sure the checkbox stays red? Any help is greatly appreciated!

[gkaiseril]

There are many places to place the JavaScript. Where exactly did you place the code?

[kylem45598253]

Thanks for your help! I put the script in the "Mouse Up" function. I have it set to "Run a JavaScrip" Is there a better way of doing this?