We as humans have the programming to recognise which areas of colour are "the background"
There is no little gnome that can do that inside your computer, computers are stupid creatures that can only do exactly what we tell them to do, and immediatly screw up as soon as anything is open to interpritation
So yes, you have to say the colour, it cant just select which one is the background on its own
Also, use .png, it is a far better image format created to replace .gif (PNG = Probably Not Gif :p)
There is no little gnome that can do that inside your computer, computers are stupid creatures that can only do exactly what we tell them to do, and immediatly screw up as soon as anything is open to interpritation
So yes, you have to say the colour, it cant just select which one is the background on its own
Also, use .png, it is a far better image format created to replace .gif (PNG = Probably Not Gif :p)