Navigation Button

Is it possible to change the default navigation button colour(white) to a different colour specified?

What Navigation Button do you mean?
You can only change the appearance of elements inside the web site and not from the browser, in case you meant the Browser Back and Forward button.
For html elements (which is what Vaadin components essentially are made of on the client) you can use css (scss) so things properties like color, background-color, …

Hi what I meant was like I want to change the color white to a different colour in the buttons in the below screen
16050.png

To be clear, those are NavigationButtons from the TouchKit addon. Yes, you can change the color with CSS:

.v-touchkit-navbutton {
   background-color: #ccc;
}

You will also need to specify your own theme if you don’t already have one.