Most anglers change lures when they get bored, not when the fish ask for it. In Kuwait the signal usually arrives long before the boredom: a tap with no hook-up, a fish that follows and turns away at the boat, or twenty casts through good water with nothing. Read them and you know when to open the box.
A single bump and nothing else is the clearest sign a fish is interested but not committed. Before you swap the lure, change the retrieve: two sharp twitches and then a pause of three or four seconds. Hamour and shaem around Kuwait take lures on the drop more often than on the burn. If the same bump repeats in the same spot without a hold, the fish is seeing too much body, so drop one size or move to a slimmer profile.
A fish that trails the lure for ten metres and turns away has decided it is looking at plastic. That is the moment to change. Two fixes solve most of it: drop the leader from 0.40 mm to 0.30 mm so the lure rides higher and swims more freely, or move from plain silver to a trace of chartreuse or pink. Clear water in Kuwait Bay and off Failaka makes fish line-shy, so leader diameter matters as much as colour.
Carry two of each colour, not ten of one. A box with forty identical minnows is a box with one lure in it.
When fish are keyed on small bait, going down one size saves the trip, while going up a size only pays when you are hunting big fish and can afford a blank. Around Shuaiba and Fahaheel the bait in late summer runs 5 to 7 cm, so a 9 cm minnow beats a 13 cm every session. In winter, when zubaidi and shaem are chasing bigger shrimp and small fish, the larger profile earns its place.
Before you open the box, cast in a different direction. Fish sitting on a depth change or the edge of a reef learn the lure that keeps arriving from the same angle and refuse it. From a small boat or kayak off Fahaheel, a drift of thirty metres turns a dead mark into a live one.
If three lures and two retrieves produce no follows in twenty minutes of good water, the lure is not the problem. Check the tide, because a slack hour fishes badly everywhere in Kuwait, and if the sea state is building, go home instead of opening another box. Log what you threw, where, and what happened in the catch log on B7R so the next trip starts from data instead of memory.
Stop guessing at the box and start reading the water. Download B7R free on Google Play, check the tide for Shuwaikh and Shuaiba and the sea state before you leave the dock, then let the fish decide when the lure changes: https://play.google.com/store/apps/details?id=com.q8dm.b7r