Seeking low plants for the front row of my flower bed, I chose "Festuca Blue" fescue grass and "Angelina" stonecrop. Both work nicely with my blue-purple-gold color scheme. Festuca Blue fescue grass, not surprisingly, provides some blue; Angelina stonecrop has golden-green foliage.
Festuca Blue fescue grass (Festuca ovina 'Glauca') is an ornamental grass. It's easy enough to trim, should it outgrow the place I have chosen for it. Angelina stonecrop (Sedum rupestre 'Angelina') is a trailing plant. The latter, incidentally, is also an excellent choice for rock gardens, as it is a drought-tolerant plant.
Remember, I'm starting out with immature plants: they will "fill in" as time passes.
In Step 8, I'll discuss my plant selection for the middle row, in which I'll use plants with blue flowers and purple flowers....