Hello, this is a good question!
There is no difference in the pattern for kimono and yukata, only in the lining and the material used.
Yukata will always have the standard/short/mid length sleeve, where formal kimono may have longer sleeves to show formality. Since yukata cannot be formal at all, they always have short sleeves.
They are universally made of cotton, generally with a large print. More high-quality yukata are made of a particular cotton with an open weave that gives it a sort of checkered appearance. The cotton is stiff and has structure to it, it’s not like jersey, t-shirt cotton or bedsheets. I’d say it’s most similar to the material a summer-weight men’s dress shirt is made of.
They are also completely unlined, being worn in the hottest summer months with only the minimum of undergarments.
Good luck and have fun!