The product is not like the sample I had seen.
'Campione' — cam-PYO-ne. Three syllables.
Use when you bought a product based on a display sample (fabric, tiles, paint, food) and the delivered item differs in colour, texture, or quality. This is a strong legal claim.
'Come il campione' means 'like the sample'. 'Avevo visto' is the pluperfect — 'I had seen'. This implies the sample pre-dated your purchase and formed the basis of the contract. Under Italian contract law, goods must conform to any sample shown to the buyer.
Il colore è diverso dal campione.
The colour is different from the sample.
Specific to colour discrepancy.
La qualità non corrisponde a quanto mostrato.
The quality does not correspond to what was shown.
Formal and general.
Ho una foto del campione.
I have a photo of the sample.
Essential evidence.
In Italian furniture and interior design shops ('arredamento'), ordering from samples is standard. Differences in batch production are common but not acceptable if significant. Keep photos of every sample you approve.