no expert but if I'm only using the traditional wear I usually have yukata one as more casual everyday/ hot weather/ onsen wear and the other one for everyday, formal, party or cold weather (since more layers)
as for festivals I think both are okay in suitable weather
and colors I actually tend to dress older sims more bold and vibrant because young and pretty are pretty in anything i don't feel they need to go the extra mile to be fashionable
but also yes grey and beige grandmas and grandpas are also present where the sims are more eco friendly and less fashion forward