Go bold. Like paint to an artist, an overwhelming amount of thread colors is both inspiring and enticing. Within thread offerings, there also reside thread that has been dyed to produce special effects. Knowing the properties of these threads, which can often be achieved by doing a sample stitch out, will enable you to offer your customers colors and effects beyond the ordinary. And, in some cases, using a single ombré to achieve a shaded effect can save time and money.
Consider doing a camouflage design using only one spool of thread, which ranges in and out of darker and lighter shades of the same color. Or a flower that is shaded and random, based on a single spool of thread. The color block trend can be picked up with a single spool of multicolor thread that will stitch out in one solid, then change to another arbitrarily, and continue changing. Color blocking in larger areas can be done with multiple colors and more choices, but if budget is limited and design is the goal, explore what some threads can produce all by themselves.
Fluorescent colors are also popular and require no special setup to produce great results. You might even mention that the makeup of the fluorescent polyester thread will cause it to glow under ultra-violet light. For a theater or dance crowd, the effect is pretty awesome. Bold or neutral colors for the more modest, down to earth, can be used in large areas to enhance a color-blocked design, keeping it on trend and unique.