Forms checkbox color setting with Gantry5 template

Hello,
With Joomla 6 template Gantry 5 Helium and the last paying version of Forms, I'd like to set the color of checkbox.

I can set the custom scss of my template, and I tried some propositions of this Forum but nothing works.
https://www.balbooa.com/help/forums/forms/design/change-label-colors-of-specific-input-boxes : not work
https://www.balbooa.com/help/forums/forms/checkbox-color : not work

Thank you for help !