Changing menu colors
To change menu text colors, navigate to Mikado Options > Header > Header Skin and make sure that the Default header skin is enabled. Depending on your theme, you might either see "Default", or only a blank space, which is the same as "Default":
You will then be able to change the menu colors. Settings for this are in some themes located in Mikado Options > Fonts and in others in Mikado Options > Header.
If you have the Light header skin, the menu text will always be white, and your custom menu colors set in Mikado Options will not take effect. Similarly, a Dark header will always have black menu text.
If your menu colors are still not taking effect, then check the setting on your page, under Mikado Header, and make sure that it's set to Default as well. Page settings override settings in Mikado Options.