A pop of color is best done with well selected accessories. In the example above a purple sweater and white shirt are worn with a simple gray suit. These pieces can be found anywhere and are in most men's closets. It is the scarf and pocket square that make this outfit noticeable and unique. The yellow, blue & purple are found in the scarf and the pocket square, but in different patterns. They play with each other without looking like a pre-planned set. There overall appearance would also be minimized once the outfit is worn, but the pops of color are still quite noticeable and pleasant to the eye.
It must be noted that all of the items have classic styling and by themselves would not be memorable. Only when they are put together do the items pop. The purple background of the sweater is key too, since it is a complimentary color to the yellow and works in both the pocket square and scarf. The colors in this outfit all work off the color wheel, which is a key to making sure the pop of color matches and not clashes.
This outfit would also work with a plain yellow scarf and a purple & yellow pocket square. Simplicity may be more the style that you prefer, which is always a classic.
When looking for a pop of color, think classic styles, simple basic colors and keep them complimentary. In formal or casual wear, this concept will work great. Sprezzatura is all about keeping people on their toes with colors, style and wear.