What Urban Sketchers Get Wrong About Colour
- Blog
- April 27, 2026
- 19 mins
If you have ever finished a sketch and felt like something was slightly off with the colour, even though you tried hard to match what you could see, you are not alone. It is one of the most common frustrations we hear from sketchers at every level. Complete beginners, experienced painters, people who have been working with watercolour for years. The feeling is the same: the colours look right individually, but the painting does not quite hold together.
Here is the thing though. The problem usually is not the colours themselves. It is what you are matching when you choose them.
The two things colour does
When you look at a building and see that it is orange, you are seeing what painters call local colour. It is the actual hue of the thing. The terracotta wall. The pink boat. The yellow facade. Local colour is what most people try to match when they paint.
But there is a second quality to every colour that carries far more visual weight, and it is the one most sketchers overlook. It is called tonal value. Tonal value is simply how light or dark something is, regardless of its colour. A pink building and a grey wall might have completely different local colours but sit at exactly the same tonal value. A bright yellow facade in direct sunlight and a deep blue shadow under a bridge sit at completely different values.
Here is why this matters.
Why value beats hue
A painting with accurate tonal values but slightly imperfect colours will read clearly and feel convincing. The viewer’s eye understands the light, the shadow, the depth, the structure.
A painting with perfectly matched local colours but muddled tonal values will feel flat and confusing, no matter how carefully you mixed the pigments.
This is counterintuitive, and it is worth sitting with for a moment. You can get the colour slightly “wrong” and the painting works. You can get the colour perfectly “right” and the painting falls apart. The variable that matters most is not hue. It is value.
What this looks like in practice
There is a moment in Ian Fennelly’s Italy course that illustrates this beautifully. He is painting the fishing boats on the slipway in Riomaggiore. One of the smaller boats is a pale blue colour. He paints it using Prussian Blue with a little white. It looks completely right on the page.
But then he says something that stops you:
"The colour of the boat is probably an ultramarine blue, but that's not important. It's not the actual colour, it's the value of it that really, really matters."
He is not trying to mix the exact blue of the boat. He is matching how light it is. The tonal value. And because the value is right, the colour reads perfectly, even though it is not a precise match.
This is something he does throughout the course. The orange building does not get painted with orange. It gets treated with Burnt Sienna and Green Gold. The pink building gets Cadmium Red lightened with white. The deep shadow in the archway gets the complementary mix pushed towards its darkest value. All from a small family of colours, all sitting at the right tonal value, all feeling connected to each other.
Why this changes how you choose your palette
Once you understand the distinction between local colour and tonal value, something interesting happens to your palette.
You stop needing ten or fifteen colours to match what you see. Instead, you can work with a much smaller set, sometimes as few as three, and match the values instead.
Ian works with exactly three colours per workshop in the Sketch Italy course. One from each primary family: a blue, a warm colour, and a third to complete the mixing range. From those three colours plus white, he produces everything you see in the finished sketch. The rich terracotta of building facades. The deep shadows in archways. The soft grey of stonework. The shimmer of Mediterranean water.
The three-colour limit works precisely because it forces you to match value rather than hue. You cannot match the local colour of everything with three tubes of paint. So you stop trying. And what you produce instead is a painting where every colour shares the same tonal DNA, where the shadows belong to the highlights and the mid-tones stitch everything together. A painting that holds together not because every colour is correct, but because every value is.
The exercise that makes it click
If you want to experience this for yourself, try this the next time you paint.
Before you start, choose just two colours that sit opposite each other on the colour wheel. Burnt Sienna and Ultramarine Blue is a wonderful starting pair. Mix them together in roughly equal amounts. Add a touch of white. What you get is a soft, neutral grey that came from the colours already in your palette.
Now use that grey for your shadows and mid-tones. Use your two original colours for the warm and cool passages of the painting. And see what happens.
You will find that the painting holds together in a way it might not have before. Not because you matched the scene more accurately, but because every colour in the painting shares something with every other colour. They all came from the same small family.
That is the shift. Not better colour matching. Better value matching. And a palette small enough that unity happens automatically.
Why this matters beyond any single painting
The lovely thing about understanding tonal value is that it goes wherever you do. It does not matter whether you are painting a Mediterranean harbour or a street corner near your house. The principle is the same. Match the value. Let the hue take care of itself. Work from a small palette and let the mixing produce the harmony.
It is one of those ideas that, once you see it, you cannot un-see it. And your sketches will be better for it from the very next time you pick up a brush.
Ready to learn more?
The Sketch Italy course, filmed on location in Riomaggiore on the Italian Riviera, opens in 3 days. It features five complete workshops, each using a different three-colour palette, and you can watch Ian apply the tonal value approach across every single one. Keep an eye on your inbox for more details soon.
What Urban Sketchers Get Wrong About Colour
About the Artist
Ian Fennelly focuses on capturing urban spaces and environments by drawing the places where people have been without actually including them.
His process involves layering watercolors, brush pens, and liners to build depth, texture, and detail, allowing them to fully immerse in the scene while adapting to changes in their surroundings.
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