I tend to like a lot of blues and purples, and typically in gradients. Here are some resources I like to use to pick out colors and gradients. I tend to use a few different tools for this instead of using only one because different tools have different featured color palettes/gradients.The variety helps.
color-hex—This one has helped me a lot because for any color, it shows you the range of lighter shades and darker shades, and what other color contrasts it the most.