Grey flags on a ground of one colour
1 of the 254 flags in the world is painted in grey and was measured on a ground of one colour. It is the only one.
One box different
The same two questions, answered another way.
How a flag gets onto this list
Both halves are taken off the picture rather than from anybody's description of it. The shades beside each flag are what it is really painted in, and they are why it is filed under grey.
The shape is the second half: The fly edge and the foot are one colour, and the same one — whatever else is drawn on top of it. That is a measurement of a drawing, so if one of these looks wrong to you, it is that sentence you are disagreeing with — and the flag is right there to argue with.
Open the finder to add what was on it as well.