Walk down a street with no brief and you see what everyone sees: the obvious subjects, the incidents, the faces. Walk the same street committed to *red* and the street rearranges itself — postboxes, brake lights, a butcher's awning, one woman's coat at two hundred metres. Nothing changed except your attention, which is the point: the constraint does not limit what you can shoot, it *reveals* what you were filtering out.

There is a name for the underlying effect — once primed to look for something, you find it everywhere. By week three of a colour month the priming is involuntary: photographers consistently report seeing their colour before they see anything else. That rewiring is the actual product of the project. The photographs are evidence it happened.

Red is the generous choice on British streets: postboxes, buses, shop signage, warning paint, brake lights. High availability, high contrast, reads powerfully even in small amounts.

Yellow is rarer and therefore sharper as a discipline — high-vis, road markings, sale signs. Scarcity forces better frames.

Blue is everywhere but diffuse (sky, denim, corporate signage), which makes the discipline compositional: the challenge is making blue *the subject* rather than the wallpaper.

Green skews natural — parks, market produce, pharmacy crosses — and pushes you towards the collision of natural and artificial greens.

Whichever you choose, decide the rule's strictness on day one: must the colour dominate the frame, or merely appear in it? A strict rule produces a tighter set; a loose rule produces more keepers. Both work — mixing them mid-month is what ruins the series.

The failure mode of colour projects is the checklist: thirty frames of red things, photographed because they were red. The escape is to keep asking the street photography question inside the constraint — where is the light, where is the moment, where is the person? A red umbrella is a fact; a red umbrella crossing a grey junction into a shaft of light is a photograph.

Edit at month's end for *range within unity*: the set should feel unmistakably one project while covering scale (a wall of colour down to a single detail), distance, and mood. Fifteen to twenty five frames is the natural size. Sequence so the colour pulses — big hits spaced by quiet ones — rather than shouting continuously.

And expect the strange afterglow: the month ends, the seeing does not. Most photographers keep the heightened colour awareness permanently, which quietly upgrades every project that follows.