I realised this now after changing the structure to flexbox.
So, if you go on my site on a tablet or mobile device.
1. Click on the menu.
2. Choose the 2nd the option.
3. then choose the library option.
4. then go back to the menu (when the page is loaded), you will see the 2nd option menu is in a darker colour. (i don’t want it a dark shade of colour)