There are no rules on how many colors you should and shouldn’t use as your palette, but there is a bit of magic to keep it simple.
For instance, green and coral. Then add a metallic color. For example, silver, gold or rose gold). Once we’ve honed in on these three, we are free to add shades of those colors three selections. For example, light coral, dark coral, light green, forest green, etc. Varying shades of the same color is very visually interesting without making the palette too busy. In the end, you’ll have a palette of about five different colors including the shiny metallic option.
Starting with three main colors allows you to reign in the look. From there you can add lighter and darker options of those colors for visual interest with cluttering the look.
Note: Tread lightly if using more than 3 main colors in your palette. If your floral arrangements are multicolored, be sure to keep all the other details neutral (white, black, tan or any metallic color) to tone down the explosion of colors.
Look to your closet or your living room for clues. Most people are consistent with their choices. If you gravitate to blue and white, for instance, it’s most likely you will buy blue and white clothes and furniture/pillows/drapes in that same palette.
Use the process of elimination. Gather all your ideas and select out your least favorite first. Keep 2 main colors and add the metallic hue.