Understanding Undertones: Why Your Gray Looks Blue
You picked a gorgeous gray from the paint chip wall. You painted the whole living room. And now it looks… blue. Or purple. Or green. Welcome to the world of undertones — the hidden pigments lurking beneath every “neutral” color.
What Are Undertones?
Every paint color is created by mixing pigments, and the secondary pigments that give a color its subtle bias are called undertones. A gray might be mixed with blue, green, purple, or brown pigments — and while the color still reads as “gray” on a tiny paint chip, those undertones become unmistakable on a 12-foot wall with natural light bouncing around.
The Most Common Gray Undertones
Blue undertone: Stonington Gray(Benjamin Moore) — looks cool and airy in north-facing light, but can feel cold in rooms without much natural light.
Green undertone: Revere Pewter(Benjamin Moore) — in certain lighting, warm grays with green undertones can look almost sage-like. This is especially common with greige colors.
Purple undertone: Agreeable Gray(Sherwin-Williams) — some warm grays carry a slight violet cast, especially under LED lighting.
Brown undertone: Balanced Beige(Sherwin-Williams) — these “greige” colors are the most popular neutrals because the warm brown undertone prevents them from feeling cold.
How to Identify Undertones
1. Compare against a true reference. Hold your paint chip next to a piece of pure white paper. The undertone will suddenly pop — you'll see the blue, green, or purple cast that was invisible in isolation.
2. Look at the darkest shade on the strip. Paint chip cards typically show four to six shades of the same hue. The darkest shade on the strip reveals the undertone most clearly because the secondary pigments are more concentrated.
3. Test in your actual lighting. Paint a large sample (at least 2 feet square) and observe it at different times of day. North-facing rooms amplify blue undertones. South-facing rooms warm everything up. LED bulbs add blue cast; incandescent bulbs add yellow.
Why Lighting Changes Everything
The same gray will look dramatically different depending on the light. A north-facing room receives cool, indirect light that enhances blue and green undertones. A south-facing room gets warm, direct light that can make the same gray feel like a warm beige. This is why painting samples on your actual walls is non-negotiable.
Choosing Safe Neutrals
If you want a gray that truly reads as gray in most lighting conditions, look for colors that designers call “balanced grays” — shades where no single undertone dominates. Browse our gray color family to compare hundreds of grays side by side and spot their undertones before you buy.
You can also use our color compare tool to put two grays next to each other and see the exact Delta E difference — if two grays have a Delta E under 2.0, most people can't tell them apart.