This is by no means a good cosplay-level ref or anything, but I figured I could talk a little about how I envision the uniforms in Sinfonia. Since the game takes place during the autumn season and I have limited resources to produce sprites, the winter uniforms probably won't make an appearance in the game.
All official school clothes
a. Autumn / late spring uniform | b. Night gown (socks optional) | c. Winter uniform (without jacket) | d. Winter uniform (with jacket on)
Winter/late spring uniform
The uniform seen in the game. All students must wear the uniform during classes and when visiting the town, but are somewhat freely allowed to wear things over and under their clothes. Furthermore, after late September hits in the boys are allowed to start wearing their winter uniforms if they want to, and everyone must wear them by the end of October. Sinfonia takes place in mid-August to mid-October, and as a result I most likely won't be upgrading the sprites of the characters - even though they're high likely going to be wearing at least longer pants and jackets over their shirts as the weather gets colder.
The basic uniform. The length of the shorts and socks usually varies a tiny bit, but shorts are usually just below knee and socks to mid-calves. Shorts, suspenders and the ribbon are all black.
The accurate colour of the shirt is something between natural and cream white. However, some students (like Rick) use old clothes of their seniors as a way to save in expenses, but as a result the clothes can be more yellowed in color. Boys who spend a lot of time outside also tend to notice their shirts turning darker in color with time.
Students are allowed to have personal clothing accessories, as long as they are not particularly distracting and don't hide their their ribbon when they're downtown. Most boys usually wear a sweater over their uniform to stay warm or to avoid dirtying the clothes.
Claude tends to wear long scarves, while Jonathan often wears a knitted jacket over his shirt. Personalized accessories often help giving the students a sense of individuality despite the uniforms and dressing codes.
They generally have 2-4 spare pairs of shirts and socks depending on their family's wealth, and usually at least one extra pair of shorts as well. Some boys prefer to switch to casual clothes after school in order to avoid dirtying their school clothes, but most don't bother.
Although all students must follow the clothing code, there is a lot variation between how exactly the boys wear their uniforms. Some keep them in perfect condition, while others rebels and keep their ribbon open or their suspenders unevenly - or both, like Leon.