I created a pattern in Illustrator and now I want to export as a PNG including the artboard which is grey. The problem is that the background won't save as grey in the PNG, it's either black, white or transparent. Does anyone know how to save the grey background as well in the PNG? (pattern is just an example)
To use a colored background actually make a colored background.
Place a rectangle of color over your art board and behind your other objects.
The art board is not supposed to be viewed or provide colors. It is considered neutral, behind the scenes, like the actual canvas surface behind a painting.