Roof colour is a large decision disguised as a small sample. You approve a rectangle on a desk and receive an entire slope above the house.
Start with what will not change
Put the shingle choices beside the actual brick, stone, siding, and window frames. Start with those fixed materials rather than a freshly painted inspiration photograph. A warm brick and a cool grey roof may create a contrast you like, but it should be a deliberate one.
Look from the distance where the house is normally seen. At a roof selection in Thornhill, the dark sample looked almost plain beside the brick on the porch. From the opposite pavement, a large sample board showed how much of the steep roof would become one dark shape. We kept it on the shortlist, but the owners could finally compare the whole house instead of judging a rectangle beside a flowerpot.
Use more than the smallest sample
IKO’s shingle selection guidance recommends looking at full-size samples and viewing combinations outside. Ask to see the actual product blend, and a completed roof in that product where possible. Screen colours are useful for narrowing options, not approving the final shade.
Compare in sun and overcast light. On that house, the lighter candidate had a greenish cast that only became obvious against the stone on a cloudy afternoon. We narrowed the choice to two actual product blends and wrote down the exact product and colour on the approval. A neighbour's roof is useful evidence only if you know what is on it; several manufacturers have remarkably similar names for quite different greys.
Keep appearance separate from performance
Do not use visible lightness alone to promise lower cooling bills or winter savings. If thermal performance matters, compare documented ratings for the specific products and discuss the roof and attic as a complete assembly. Our aesthetic preference is the shade that belongs with the materials staying on the house. The best colour is not always the one that looked best by itself.