Usually we don't think of herbaceous perennials as having fall color. However, there are a select group of perennials that might surprise you with their brilliant foliage colors in fall.
Yellow Fall Color
Yellow is the most common color for fall foliage on perennials. In fact, the leaves of many perennials will turn yellow before they go dormant or disappear for the winter. For the best yellow fall leaved perennials try: Blue Stars, Balloon Flowers, Ferns, Hostas, and Monkshoods. Almost all Blue Stars, Amsonia tabernamontana (Blue Star), Amsonia ciliata (Downy Blue Star), and Amsonia hubrechtii (Arkansas Blue Star) are famous for the clear yellow foliage fall color. The Downy and Arkansas Blue Stars have narrow/thin foliage that also adds an interesting textural contrast throughout the gardening seasons. Some ferns that have the best yellow fall color in my garden are Sensitive Fern (Onoclea sensibilis) and Royal Fern (Osmunda regalis). Balloon Flower (Platycodon), Hostas (Hosta), and Monkshood (Aconitum) are some of the most reliable perennials for yellow fall color. They provide at least a couple of weeks of good fall color every year in my garden.
Red Fall Color
While red fall color tends to be more brilliant in the garden, it also tends to be the most variable, especially on perennials. Peonies (Paeonia), Pigsqueak (Bergenia), and Barrenwort (Epimedium) can have burgundy red foliage colors in fall. Gooseneck loosestrife (Lysimachia clethroides) often has a bronzy-red fall foliage color. In a good year, Columbine (Aquilegia) can last long enough in the garden to turn orange-red in the fall. For the most reliable red fall color, however, Bloodred Geranium (Geranium sanguineum) is your best bet. After a hard frost the foliage often turns a brilliant red color before disappearing completely a month later.
Many ornamental grasses also have striking fall color. Several Switchgrass cultivars (Panicum virgatum 'Rehbraun', 'Rostrahlbusch', etc.) and Flame Grass (Miscanthus sinensis var. purpurescens) have bright red leaves before turning tan in winter. A couple of native grasses like Indian grass (Sorghastrum nutans) and Little Bluestem (Schizachyrium scoparium) have yellow to burnt orange fall color.
That's it! Brown and tan colors don't count, making this a short list! The fall color season for perennials is equally as short, often only lasting a couple of weeks. But even brief periods of fall color are appreciated in the garden. You might be impressed with the multi-season interest these plants can provide to your garden.