Separate visual preference from function
A logo may be judged primarily by appearance. A serial number must remain readable, and a machine-readable symbol needs to work under specified reading conditions. These are different acceptance questions. Make the intended use explicit so the supplier can propose a suitable process and sample plan rather than maximizing darkness without context.
Inspect under relevant conditions
A mark viewed under a desk lamp may look different on a production line or after installation. Identify the viewing distance, lighting and orientation that matter. For camera or scanner applications, evaluate the actual reading arrangement. For a finished product, assess the mark after required cleaning or other downstream treatment rather than only at the marking station.
Keep the reference practical
Use an approved sample or defined acceptance criteria that both parties can apply. A highly compressed phone image is useful for discussion but may not preserve color or fine detail. Retain the original inspection record and clearly identify the part and finish it represents. If the requirement is dimensional or machine-readable, use the relevant measurement instead of substituting a visual comparison.