This is a color model display format that uses the three primary colors (blue, red and green) to create an image. Each color can have up to 255 gradations, allowing for color depths of up to 48 bits. RGB supports the display of 16,777,216 colors.
PBM is a Portable image in black and white. Can be opened with programs: Adobe Photoshop CS, ACD Systems Canvas 15, ACD Systems ACDSee 17, Newera Graphics Converter Pro, Corel PaintShop Pro X6. File contains 1 bit per pixel. PBM is a kind of file format PPM. And can be readable or binary.