Sub-Menu Menu Icon Color & Coloring (mobile screen size)

I am trying to change the color of the 3 lines that represent the sub-menu on the mobile version of the attached page (see screenshots). I can't work out where the color specification is, I can't find an image that may be used either?

On a similar note, I can't see where to change the sub-menu coloring of the text, background, etc?

Thanks

Mark

And one more image to help...

I haven't received an answer to this? Anybody tell me how to alter the color of this? I can't find the code....