Peppers: the tri-color combination — green, red, and yellow — is the way to go. Green adds slight bitterness and body; red and yellow bring sweetness and visual brightness. Sherry: use a dry fino or manzanilla, not cooking sherry — quality matters here. Potatoes: fold in at the very last moment to preserve crispiness; they should contrast with the saucy chicken, not disappear into it. Saffron: bloom in warm sherry for at least 5 minutes before adding — subtle but essential to the Spanish character of the dish.