Changing the colour of the plus sign in the drop down in the accordion menu

txt2nite

Hello again,
How do I change the colour of the plus sign '+' on my left hand menu. Its currently grey, but I'd prefer for it to be white.

My website
https://shop.tubemapper.com/

regards

Hikin' Mike

.sm-accordion-item-action .sm-fonticon::before {
  color:white;
}