I think the most common question clients have when booking photos is what to wear. It is an important subject too, because the wrong color and pattern combo can terrorize otherwise beautiful images. If all subjects are in the same color, or similar colors they subjects will blend together. Too many patterns and colors that don't go together also do not make for pleasing images. This beautiful family did such a great job! They achieved a perfect balance of colors.
I usually begin with a Children's item of clothing, because those are usually the ones with more colors to work with. Adult clothing tends to be less colorful. For our holiday maternity shoot, I dressed my son in this amazing shawl collar reindeer sweater from Cat and Jack. It was Blue Green with cream reindeer, and turquoise and dark grey accents. It was busy enough, so I did jeans to finish off the outfit and a white undershirt.
I then moved on to my outfit. I chose a dark grey dress with a subtle white pattern. I finished the outfit with a couple simple pieces of turquoise jewelry and dark grey opaque tights. My husband wore a green plaid shirt with turquoise accent colors and jeans. It made for amazing pictures!
Basically the ideal image for four people will have two people in patterns complimenting each other. Maybe one Hawaiian shirt for Dad, and a matching striped dress for his daughter. Or perhaps the Son is in a plaid shirt and mom is in a flowered dress with matching colors. The other two people should be dressed in solids with colors picked from the patterns. Using shawls, scarfs, hats, hair accessories, and jewelry can help add color balance. For a 5th person, keep with solids and then if you are adding in a 6th person throw in another pattern complimenting the others.
This coming from a former visual coordinator in the retail industry. I hope this helps you pick outfits that are amazing and complimentary to each other for your next photo session!