Drop down menu on home page is visible but not visible on other pages

I am very new to web development. I am trying to develop a website using Word press Astra them. Its basic Astra them and not PRO. The problem i am facing is..... The drop down menu is visible on my home page but not visible on other pages. Its white (Text color) and white background may be that's the issue... My query is how to change background color and text color in word press Astra them on other pages other than home page. Thanks you!