Read about quilters and color. Years ago Jenny Beyer had a vhs tape out and she showed samples if you match to exactly quilts look flat. Match the colors and then go just darker or lighter on some of them.
You get better by trying so make a series of small quilts. Or analyze quilts you love and dissect the underlying pattern off color. I recommend Joan Wolfram's 3 in 1 color tool.
http://joenwolfrom.com/color-design-tools/ I use it to understand what might work on something I am envisioning. or I use the tool when I am trying to add fabric to project - yes, I can do it by bringing swatches with me and walking among bolts of fabric, but the tool helps me get into the range I want quicker.