Answer: White.
When adding all the three primary colors at maximum intensity, the color that will be produced is the color white. This is applicable when using the color scheme of computer programs like Adobe Photoshop, GIMP, etc. You will only get the color white when using the additive color palette in the RGB mode. If you are using the subtractive color palette in the CMYK mode, you will end up with the color black when all primary colors are at maximum intensity.