When I tell people I make yukata, most people have no idea what I am babbling about. You say kimono, and most non-Japanese people at least have an idea about what you’re talking about, but yukata? Not so much.
Yukata were originally robes worn at hot springs, much like dressing gowns or smoking jackets here in the west. As time went on they became clothing in their own right, often worn at home or summer festivals. Think of them as the blue jeans of the kimono family; appropriate for play and outside work, but you can’t wear them to a black-tie affair^^
For a long time yukata were almost always made of cotton, with white, blue or bluish gray patterns. Now they are made in a variety of bright colors and patterns, ‘though cotton is still by far the fabric of choice. Most men’s yukata are still fairly plain, with geometric or water-themed prints, whereas women’s yukata are often floral patterned. Children’s yukata can end up having just about anything on them, from solid colored to toys, Mickey Mouse and Hello Kitty-chan.
Yukata are actually seeing a return to popularity by younger generations, possibly because they are easier to wear and care for, and have fewer ‘rules’ on proper patterns and colors, than formal kimono. Plus, being cooler than even shorts and covering your arms and legs so they don’t get burnt to a crisp is a definite attraction!