Tactical Scud DJA27 BL in orange color it represents a completely infected scud. It is probably the most successful color for trout and grayling. Orange colored gammarus insects are usually weakened and unable to swim fast enough to defend themselves from predators. This is the reason why orange color is so effective for these flies.
More about scuds:
How to choose the color: dark colors for rivers with peat and stones covered with brown algae, light colors are for rivers with limestone and algae or green aquatic plants.