FAB
A foam-arsed buoyant attractor that can hold up a team, suspend nymphs, or act as a bright trigger in its own right. It is less a natural imitation than a tactical device: depth control, visibility and provocation in one small blob of trouble.
Spring and autumn in stillwater when pulling attractors. Fish on a floating or intermediate line with aggressive strips.
The foam tail adds lift, pause and hang time, while the bright body gives trout something obvious to react to. It can draw takes itself or make the flies around it fish better by controlling depth.
Starting points, not rules — depth, presentation and size usually matter more.
Sunburst, coral and orange are common searching colours, especially for active or recently stocked trout. Try black or claret under heavy cloud, and biscuit, peach or pale pink in clearer water or once fish have seen a lot of bright FABs. A two-tone pattern is worth trying when no single colour is working.