If as you said the Color only went wrong once since you pressed the button. Thats once too many times.

I say hit the button very other day not once per week as I said earlier
This will clear the problem eventually

(I'm sounding like a Doctor

)
And the black "border" you mention is supposed to be there! Your screen will look very odd when you use a program that uses the full screen area

Ideally the border area width (default) is the same size as the toolbar with the Start Button and Clock As you have an Older monitor you'll have no On Screen Display and no Reset to Defaults button

It is only by trial and error you can return the display to its original state,a TV repair man could do it or computer guy...But You won't do any harm by having a go yourself and gain a bit of experience

Only target to aim for the border should be the same width all the way around

and parallel not tilted
Tip: Measure some "Finger width" paper strips out and tape them to make a frame (a dummy border)
inside the monitor screen this will act as a template to help get things balanced up in lieu of the missing default reset button
