Unknown Space in model

I am trying to apply a color to an area on my model and a white streak shows up where it should be solid color as shown here:

Here is a view of the underside of the same area, I checked to see if maybe I had a couple of stray lines, but as you can see there is none. What causes this?

It would seem all you want is a simple solid color material.
But the unwanted streak appears to be the result of using a Texture Image

Click … Window > Materials > In Model (little house icon)
There, select the material in question and then click on the Edit tab
There, deselect Use Texture Image
Then click… Window > Model Info > Statistics > Purge Unused

Try this…
Switch All Layers ON
Also View > Hidden Geometry > ON
I think your issue is that you have some unexpected subdivision of the surface by off/hidden geometry…
Also ensure nothing is unexpectedly sub-grouped…
Apply the material to faces, not groups or component-instances…

Always put ‘raw’ geometry on Layer0.

But why not post your SKP with the issue so we can be sure…

Geo, it worked eventhough it was a color I imported from a separate texture file on my computer. Thank you.