You have the ability to use a CSS media query to alter styles based on the screen size.
If your navigation bar is composed of an svg element (which seems to be the case), you will need to utilize the appropriate css properties like fill
to modify its colors.
Take a look at this example. Resize the screen and observe how it transforms.
.navbar {
fill: black;
}
@media screen and (max-width: 800px) {
.navbar {
fill: red;
}
}
<svg class="navbar" viewBox="0 0 100 80" width="40" height="40>
<rect width="100" height="20"></rect>
<rect y="30" width="100" height="20"></rect>
<rect y="60" width="100" height="20"></rect>
</svg>