I'm a big streamer guy....always have been!
There's just something about stripping the fly and feeling that grab that really gets the juices flowing. I not only love to fish them, but I really enjoy tying them as well. Not only are they on the larger side and often relatively easy to tie, but they lend themselves well to experimenting with things like color and weight. While many nymphs and dries are close imitations of the real thing, a lot of streamers are more of a general "attractor" or "suggestion" of something that's alive which also opens the door for even more creativity on the part of the fly tyer.
I keep my streamers relatively simplistic both in coloration and in the actual construction. There's surely a lot of different ones out there, but I have never felt it necessary to over-complicate things by tying a ton of variations and styles. I've built confidence in several types over the years and tend to stick with those as my bread and butter confidence flies.
With that said, I'd like to share two quick design elements that I incorporate into some of my streamers that I feel improves my success rate to some degree.
Contrast: Being an avid conventional bass angler since my teen years has taught me a ton regarding color selection. Knowing what colors to use under certain conditions has helped my fishing success in not just bass fishing, but also in every facet of angling beyond. Like most bass anglers, I choose my colors carefully based on both available forage and the current conditions. Whether I'm just trying to get my offering noticed or want to actually imitate something very closely, I always try to incorporate some type of contrast. I am a firm believer that it can often have an impact on my success. In my mind, the same goes for flies!
Think about the typical spinnerbait a conventional angler throws for bass. While a particular model may feature a solid white skirt and head along with silver blades, I always gravitate towards something with a bit more detail and contrast. This may be as subtle as a pair of red-painted gills and some strands of blue and grey silicone mixed into the skirt, or as drastic as a 50/50 two-tone skirt and painted blades. That depends on what I'm imitating and the water color.
An offering that features some visual differences rather than just one solid color throughout has more depth, detail, segmentation, and thus gives me added confidence. I mean, it can't hurt, right?
Very common streamer flies like woolly buggers, clouser minnows, and general baitfish streamers are the ones I most often see tied in one solid color scheme. They'll surely catch fish to some degree, but I feel I can up the odds by shying away from that. I tend to not go overboard with crazy and abrupt contrasts and detailing, but putting in little subtle differences (that are actually noticeable) or using colors that compliment each other in a natural way can really set off these flies.
This can be as simple as using black hackle and thread on an otherwise olive woolly bugger, or using a gray/white clouser with red dumbbell eyes in place of an all-white one with unpainted eyes. The possibilities are endless. In flies that can incorporate dubbing, that's also a great material since it can be blended to create a unique body tone to contrast with the other materials.
Coloring the Tail: I've recently become somewhat addicted to tying EP-style flies and using permanent markers to add detailing. These types of flies can look pretty good in standard form, but using some markers to add extra detail or improve the color contrast of the fibers helps a lot to increase realism. One extra little thing I like doing sometimes is coloring a small bit of the tail, too. Especially on flies using lighter-colored fibers, it can help provide a more visible profile and accentuate the swimming action of the tips. If you look up pictures of various baitfish and forage fish online, many of them have a contrasting tail color anyhow, so this just makes sense.