Autumn and the red leaves could symbolise a lot more than merely that being the time of her awakening.
Beauty, decay, death, possibly the hope of renewal, the unstoppable marching of time that is slowly guiding us all towards an inevitable death.
Oh and Belle Époque France (1871-1914) which this game openly states was it's inspration was rather dominated by Art Nouveau which was at peak popularity during the latter half of that period. Which was characterised by organic things such as leaves and flowers./
I dare also say it's all possibly leaning somewhat into the popularity of Elden Ring too, using similar visual themes. The art style Paintress in the trailer awfully resembles Marika, surrounded by a golden ring, with rocks and floating chunks of buildings. It's not so much of a stretch to think the red leaves are a nod to Scarlet Rot, itself also an clear representation of decay.

Originally posted by Ratsplat:

Any connection between red leaves and france, with painting? Perhaps the species of tree?
In the beginning you also see red being used during the festival where the oldest depart.
For now, it may just simply tell us that fall/autumn is when the Paintress awakens.

Yes, it may be just fall / autumn.

Or they are inspired by paintings of Van Gogh or other painters which especially makes sense here as its about The Paintress.