Plain colors are mostly transparent film with many shades and tones.
Remember these films are translucent so will be lighter than a computer image can show. The colours you see here are as close as possible to the actual films but look solid on the screen like they have a white backing.
Full sheet – 660mm x 460mm
Half sheet – 460mm x 330mm
Quarter sheet – 330mm x 230mm (slightly larger than A4 size)