Use this practical sequence: identify the surfaces, compare colour compositions, verify physical samples, choose a suitable coating system, then calculate quantities.
Start with what cannot change
Floors, roofs, stone, tiles, counters and furniture help narrow the palette. Compare paint against those materials rather than against a white screen alone.
Keep the evidence with the decision
Save your visual study and record the actual manufacturer, shade code, product and finish when confirmed. An image export is a conversation starter, not a purchase specification.