I've added the following styling but it doesn't remove the white border or change the color as shown in the image. Also how can I remove the white vertical line on the end of the menu?
In order to remove the white borders between the menu items, you will need to apply the desired styles to the li elements. Also, please, note that when the border-style is set to none, the border-color will not be applied as well.
As for the last vertical white line - it is not part of the default styling of the menu and I will advise that you follow the first two points in the following blog, inspecting where this style is coming from (it can be inherited by some global CSS style):
Once you know the styles you need to override, you can use the same style selector and add "html body " in front of it to make it more specific, "stronger". More on CSS specificity you can find here:
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