Can't remove grey background colour on menu button


I am reaching out as I built a new menu for my e-commerce website. I am currently facing some issue with my menu button. Basically, when I hit the cross button to close my left side menu, the original button stay in gray. I can remove this colour by clicking a second time anywhere on the page. I would like to make disappear this grey colour without requesting any other action from users. Is anyone can help me, please?

Thank you very much for your time given,

Here is my site Read-Only:

here some screenshots:
1- menu open

2- after closing menu