Situations vary a lot, making any generalization hazardous (ha - pun).
Generally speaking, and based solely on NFPA 497 guidance (without a lot of thinking), I would say:
- If there is a Div 1 inside the door, and the door is opened as part of any expected activity (no matter how infrequent), the outside would also be Div 1;
- If there is a Div 1 inside the door, and the door is not opened as part of any expected activity (no matter how infrequent), but can be opened, the outside would be Div 2;
- If there is a Div 2 inside the door, and the door is opened as part of any expected activity (no matter how infrequent), the outside would also be Div 2;
- If there is a Div 2 inside the door, and the door is not opened as part of any expected activity, but can be opened, the outside is still Div 2.
Obviously situations vary a great deal, but a rule of thumb would be a Div 1 hazloc would extend outside the door to a 3'-5' radius in all directions; Div 2 might be up to 15' all directions.
I'm not saying that the paint mixing operation would actually give rise to any hazloc, but if it did, the above would be a reasonable first approximation.