From our recent event of the fourth of July in the USA, I was also thinking of Japan's summer festivals. Besides yukata, are there kimonos that have festival themes like fireworks, festival decorations/sceneries, specific patterns, specific colors, etc.?
Japanese traditional culture is all about celebrating seasonality so indeed summer matsuri themed patterns are pretty common on summery items :)
(note that I used summer here in the Western sense of July/August. Traditional Japanese summer goes from something like May to July)
Yukata+kimono+obi+uchiwa are a staple, you can also find happi (tube sleeves coats) but those tend to bear mon (crests) and auspicious kanji.
Other festival garments count for example yosakoi (type of dance groups) uniforms, but those are more performance oriented. Otherwise, what would be a matsuri without fundoshi loincloth ;) (see how to tie one here)
On the top of my head, summer festival patterns can include (please note some are not summer only):
dashi/yatai (parade float), used during processions. Mikoshi (portable shrine) is theorically possible but I don't remember seeing such a pattern
kingyo (goldfishes), kingyosukui is a popular summer game
fuurin (windchimes), often sold at matsuri
men (masks), most often kitsune or tengu but many more exist
toys, like dendendaiko (rattle drum) for ex.
matoi (firemen poles), brigades often present acrobatic shows in summer
chouchin (paper lantern), also see Obon below
Japan holds a myriad matsuri all across the country, each with their own traditions. But big celebrations often have related patterns:
Tanabata has stars, bamboo, tanzaku, magpies, ox, etc.
Obon has lanterns, cucumber, eggplant, death themed motifs (like nozarashi or graveplates), nod to Kyoto's Daimonji kanji, etc.
Famous festivals also have their own imagery (yamaboko float for Gion matsuri ex.).
As for colors, scarlet red is often found on matsuri decors, and indigo blue is a classical summer color (yukata were once dyed with it), but tbh any can be used nowadays :)