Selecting a paint color can be very tricky. First, the sheer number of choices can be overwhelming. When I visit a client I bring fan decks for Classic Colors, Preview Colors, and Aura, along with eight rings of 2x8 Preview samples in a case that looks like this - only much bigger. All in all there are over 3500 colors to choose from. So although my job as a designer is to narrow those choices for my clients (hopefully to three), it might take just a little bit of time.
Once the color selections have been made (always in the room to be painted), clients need to see larger samples in the room - and in different locations. So I order large (8x8) paper samples that then must be put on white poster board so that the white shows around the edges. Those poster board samples are placed around the room in strategic places: the darkest wall, the lightest wall, the place where your eye goes when you enter the room from each entry - and anywhere else that is important. This usually involves placing 5-8 sample boards around the room. Then the clients need to look at the boards at all times of the day and night. Seeing the boards in direct daylight, under artificial light, on cloudy days, and at all times of the day and night (because the lighting will be different). This process generally takes at least several days. And to show why, here are three photos of three different rooms all painted in Benjamin Moore's Powell Buff.
At this point the clients may have a color selected. It's taken a lot longer than a day - or three. But the really good news? The chances are very good it's the right color. And that makes everyone happy. Except perhaps for the painter, who was looking to get paid repainting.