12 Jul 2019
If you somehow control a Diamond Knight for which no color was chosen, its last ability will never trigger.
12 Jul 2019
Diamond Knight’s ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
12 Jul 2019
You must choose one of the five colors of Magic as Diamond Knight asks you to choose a color. You can’t choose “artifact,” “colorless,” or “chartreuse.”