I love working with solids. The range of colors available is awe-inspiring. It's almost unreal how many variations of a single color we have to choose from.
Both Moda and Kaufman have sample cards available with the full line of solids available. Kaufman even has a panel of fabric available! While one of these would be awesome, I prefer to put those funds towards other fabric purchases and came up with a quick and easy DIY swatch system.
Each time I use a solid, I staple a swatch to an index card and file it in a coupon holder. Nothing fancy, but it allows me to easily match up colors, see the different shades I've used in the past, and make choices for future quilts.