Searing Rays — ruling 1

You choose the color on resolution. Your opponent does not get to respond between the color choice and the damage happening. They need to use any damage prevention they want before you choose a color.

Searing Rays : règles, fonctionnement et interactions (MTG)

Searing Rays is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Choose a color. Searing Rays deals damage to each player equal to the number of creatures of that color that player controls.

How it works : Searing Rays

Original English text — Wizards of the Coast / Scryfall

#1October 4, 2004· Wizards of the Coast
You choose the color on resolution. Your opponent does not get to respond between the color choice and the damage happening. They need to use any damage prevention they want before you choose a color.
No other card is named in this ruling.