VGA video filter and frequency requiered for this filter
For a good-quality computer video display, where fine vertical lines show the same contrast as fine horizontal lines, your video bandwidth should be able to pass at least the 3rd harmonic of the fastest square wave that appears in the image.

The fastest square wave is alternating dark/light pixels, so its frequency is half the frequency of the dot clock. For VGA at 25.175 MHz, this would be 12.59 MHz. Three times this fundamental frequency is 37.76 MHz, so yes, a 36 MHz filter would be a good choice.