The order of decisions is light, then brightness, then hue
Curtain advice usually opens with colour, which is the third decision in the sequence and the least consequential. The first is how much light the window should let through. The second is how much light the fabric sends back into the room once it is hanging. Colour matters through that second step, and only through it.
Get the first two right and almost any hue will work. Get them wrong and no hue rescues the room: thin white cotton in a bedroom facing east will wake its occupant at sunrise whether it is white, navy, or sage.
What a colour does physically: it sets reflectance
A curtain is a large vertical surface, and a large surface returns light into the room. Roughly, white and off-white return 70 to 85% of the light that reaches them, light greys and creams 50 to 70%, mid tones and saturated colours 20 to 40%, and navy, charcoal, or black 5 to 15%.
That one property explains most of what people describe as a colour's mood. A dark curtain returns about a sixth of what a cream one does; spread across a whole room the drop is smaller, but plainly visible. The room has not become energetically heavier. It has become dimmer, and a dim room reads as small.
Opacity comes first, and it is not the same axis as colour
Almost every curtain sold falls into one of three grades, and the gaps between grades are far wider than the gaps between hues:
- Colour sits inside these grades, not across them. A dark unlined cotton blocks more than a white one and is still an unlined cotton.
- One arrangement solves both halves of the day: two layers, a sheer for daylight and a blackout panel for night. No single fabric can be both.
| Grade | Light transmitted | What it is for | What it does not do |
|---|---|---|---|
| Sheer (纱) | 50 to 70% passes | Daytime privacy with the window still open to light | Nothing at night — a lit room is visible from the street |
| Unlined fabric | 20 to 40% passes | General rooms, glare control | Will not hold back a sunrise or a street lamp |
| Blackout, coated or triple-weave | Under 1% passes | Bedrooms, shift work, projectors | Removes the daytime view; needs a sheer layer to stay liveable |
The bedroom case, with a number instead of a colour
A bedroom with a 2 m² east window and thin white cotton. The occupant wakes at sunrise and cannot sleep past six. Swapping white for navy in the same fabric changes almost nothing: the same 50 to 70% of the morning light still arrives, slightly cooler in tone.
What changes the outcome is the grade. Blackout panels bring transmission under 1%, and the room stays dark at six in June. To check the result rather than trust it, put a phone light-meter app on the pillow at midnight with the room lit as usual: a bedroom reading in the tens of lux is one where the corridor light or the street lamp is doing the work, and the curtain is not.
Night-time light is the half of this with evidence behind it. Sleep guidance is consistent that a bedroom should be as dark as practical, and the mechanism is not symbolic: evening light delays melatonin release, and the effect appears at levels well below a reading lamp.
The five phases are a cycle, and only the cycle can be calculated
The colour system is a loop rather than a list, and the loop is the only part that can be reasoned with:
- A room whose two largest surfaces fall into a controlling pair — a green wall with an ochre curtain — is the one combination the system can actually object to, and it is easy to avoid.
- The step everyone skips, assigning a phase to a room or to a compass sector, is not in the cycle. It comes from a separate school, and different schools assign it differently. The cycle is arithmetic; the assignment is a convention.
| Phase | Colours | Generates | Controls |
|---|---|---|---|
| Wood 木 | Green, teal | Fire | Earth |
| Fire 火 | Red, orange, magenta | Earth | Metal |
| Earth 土 | Yellow, ochre, terracotta | Metal | Water |
| Metal 金 | White, grey, metallic | Water | Wood |
| Water 水 | Black, navy, deep blue | Wood | Fire |
Room by room, once the light is settled
With the grade chosen, colour becomes a question of what the room needs at the hour it is used:
| Room | What it needs | Colours that work | What to avoid, and why |
|---|---|---|---|
| Bedroom | Darkness, low evening light | Navy, charcoal, warm grey, muted green — all low-reflectance, which is what a bedroom wants after dark | A large panel of bright red or orange: high reflectance at the wavelength that reads as alerting |
| Living room | Light in the evening, flexibility | Warm neutrals, sage, clay | Stark white on a big window: glare by day, and it reads as a blank at night |
| Kitchen | Cleanliness, light on the worktop | Cream, warm white, light green | Dark panels at the window: you lose the light you are cooking by |
| Study | Focus without glare | Light blue, soft green, warm grey | Deep saturated panels beside a screen: the contrast tires the eye faster than a neutral does |
| Children's room | Play by day, sleep at night | Pastels with a blackout lining | Dark colour with no lining: it looks like night and still lets the sunrise in |
What a curtain cannot do
Red curtains do not attract money, green ones do not improve health, and blue ones do not advance a career. Those are marketing claims, and they are not derived from the five phases either — the cycle has nothing to say about income.
What a curtain does is set the light in a room: how much arrives, how much comes back, and what colour the room is once the lamp is on. That is a real effect, measurable with a phone, and worth choosing carefully. It is also the whole of the effect.
Disclaimer: This content is for informational and cultural reference purposes only. It does not constitute professional medical, legal, financial, or psychological advice. Readers should exercise their own judgment and consult qualified professionals for specific concerns.
Sources and review basis
Traditional references explain historical vocabulary and context. Official practical sources support only the observable safety, comfort, or environmental points noted in the article; they do not validate metaphysical claims.
Traditional reference
Huangdi Zhaijing (黄帝宅经)Wikisource digital text · Accessed 2026-07-14
Historical context for traditional residential orientation and spatial vocabulary. Modern recommendations are judged against real conditions.
Practical source
US NIH/NHLBI: Healthy Sleep HabitsNational Heart, Lung, and Blood Institute, NIH · Accessed 2026-07-14
Health background for sleep routines and bedroom conditions; it does not endorse directional feng shui claims.
Practical source
CCOHS: Lighting ErgonomicsCanadian Centre for Occupational Health and Safety · Accessed 2026-10-14
Summarises lighting levels, glare, and contrast guidance for indoor work, reading, and circulation areas.
