I can't find historical weather data for October (or any other month) in Himachal Pradesh. Is it cold? Snowy?
What would be a good idea to bring for minimalistic clothes packing?
I got this link which claims to have averaged the temperature data across months in the town of Shimla in Himachal Pradesh. It might not be snowy but expect chillness in the air - definitely at night.
I don't think you need to pack clothes to withstand freezing winter. You do not need snow boots or thick jackets. As for what you need, you could decide for yourself based on the temperature data as it is sort of really a personal choice.
If you are wondering how to decide on clothes to carry, you could refer to this link here as a starting point.
your clothing depends on your tour. Like if you are trellising to hilly areas you need to bring some serious clothes as the rain season is about to end and so the began of snow fall and in HP winter starts from September and lasts upto march.
But if you are planning to travel to areas like shimla, kasuli average clothes(average means a little warm as shimla will give you a good chill) will do the job but if you are planning to visit Rampur,Kinnuar,Manali you need to bring heavy clothes as in snowfall will start in rekong-pio when there is festival in manali i.e dusshera and if you are visiting to kangra(not that cold) but then dharamshala (one of coldest area in HP) for visiting to kinnuar pack some serious colthes and forget about pangi as the roads will be closed.
There's another thread which talks about this here: Ideas for versatile clothes in northern India
The link explains that a simple Pashmina can be versatile for cold weather, a windcheater is also useful but essentially it is possible to buy some suitable clothes that you need there, rather than packing them
Firstly, the climate will depend on the places you plan to visit, also the month of October marks the beginning of Winter in India and hence you're more likely to face the cool weather.
The cold winds of October won’t let you to wear summer clothing, specially in the evening when the sun sets, so before coming, be prepared with some of the woolen stuff. Sweaters, Sweat shirts, light jackets, cotton wear, shawls are some of the belongings that will provide warmth during this month. Light winter clothes will work during October.
It is advised that Visitors must carry strong pair of shoes for walking and touring hills as Himachal Pradesh mostly consist of hilly regions.