A coloring blanket is a soft throw with line art printed on it, ready to be filled in with fabric markers. The usual size is close to 59 x 50 inches, and the markers are often included.
There is no rule about where to start: one flower tonight, a corner of the pattern tomorrow. It is one of the few hobbies a whole household can share around the same piece.
Designs vary a lot: dense floral patterns for long evenings, bigger shapes for kids or beginners. Choosing the design is half the fun, so it is worth looking at the whole pattern before picking.
The part people ask about most is washing. According to manufacturers, washable water-based ink comes out in a normal machine wash, leaving the printed outlines ready for a new round. Check the care label before the first wash.
Some people switch to permanent fabric markers for a finished blanket they want to keep as it is. Just keep track of which areas were done with which ink.
Two small tips before you start. Lay the blanket flat on a table rather than on your knees, and put the caps back on the markers between sessions. Testing a color on a small corner first shows how it looks on the fabric.
Many adults treat it as a relaxing hobby, something to do with their hands while talking or listening to music. Once colored, it is still a cozy throw for the couch.