Checkbox Customization

Hi there,

I have for ages now been trying to customise and style the checkbox, everything else is working perfectly in terms of css selecters and styling. However, nothing seems to be able to change the style of the checkbox, i would like to change the border color for example, but it seems like no matter how i type it in css it does not go through?

I am being an idiot here and missing something obvious in terms of the selecter? Does anyone know how to achieve this?

The page I need help with: [log in to see the link]