1. Odoo 17 uses a built-in color field (0–11) for calendar views.
2. Colors are grouped automatically, but you can set them manually in Python for specific appointment types.
3. No setting exists in the UI to assign specific colors per type—you’ll need to handle it in code.

@api.model

def create(self, vals):

    if 'appointment_type_id' in vals:

        if vals['appointment_type_id'] == YOUR_TYPE_ID:

            vals['color'] = 2  # Blue

        elif vals['appointment_type_id'] == ANOTHER_TYPE_ID:

            vals['color'] = 4  # Green

    return super().create(vals)

Color codes go from 0 to 11, each representing a different color preset in Odoo.

How It Works:

The calendar view uses the color attribute to apply different background colors.

Odoo assigns colors automatically based on the value of the group field (e.g., appointment_type_id), but you can control this with a small customization.

I Hope It is Useful.