It's not often that a client is adamant about a house color.
At least not to the extent of being so fixed on one color family that all others are not available for consideration.
With that caveat, I began to look at various yellow paint colors for the exterior of a Victorian home in a Boston-area suburb.
Not only was the only option to be "Yellow," but the painting was going to be done by an area company specializing in a 'never-paint-again!' method, and so it had to be the right yellow to last...
and last...
and never be changed.
Originally built as a single family house, as were most structures of this general style, this house has been made into apartments.
And, the house was already yellow.
Selecting a different yellow for the body, with a more subdued color for the doors and an earthy color for porch floor and steps, was not a huge color change but it was a significant one overall.
The new palette: the painting company said they would tint their own product to these colors from Sherwin Williams that I selected for her:

• Body: SW 6374 - Torchlight
• Shingle accent: SW 2817 - Rookwood Amber
• Window and door casing trims, and stair risers: SW 6372 - Inviting Ivory
• Porch floors and stair treads, front and back: SW 7053 - Adaptive Shade, a stoney gray
• Front and back doors: SW 6278 - Cloak Gray, a deep plum

I had specified Rookwood Amber to be used on the details of millwork as well, which would have been a lovely detail, and would not have appeared over-decorated.
Some of the column detail was done, but other details that were to have been done on the peak trim and some of the other decorative millwork would have completed the picture.
Unfortunately this was not all done to specifications.
Ultimately of course it's up to the homeowner, who is the person hiring the painting contractor.
Sometimes the finishing touches are omitted due to the budget constraints and the result, even if beautiful, seems to be missing something.
Four quick tips

• In homes with architectural detail, consider using color in the architectural details as a way to add balance and refinement.
  "Painting out" the detail sometimes works but the inclusion of the right, subtle color can make a world of positive difference in the overall appearance of your home.
  
• Even a simple color change can make a big difference.
  In this case, where Yellow was the only color family considered, it was a matter of getting the right one to suit the building.
  
• Testing: you can see that the tiny strips of color-tests, applied close together, don't provide you with much 'information' about how the color will look on the house.
  It's important to test on large areas that you can move around the building at different times of day, on the different surfaces.
  
• Testing your paint colors on primed card stock or even pieces of wood (ideally, using siding to replicate the shadows) is a better method that small swatches.
  Be sure to test using 2 coats of any colors you are considering.