if you have no cards in hand mtg Mindstorm Crown [Mirrodin] Magic: The Gathering - Template

No, partner commanders can be different colors

712.3b While the two cards of a meld pair are on the battlefield as a melded permanent, the object represented by those cards has only the characteristics of the combined back face, except that its converted mana cost is the sum of the converted mana costs of its front faces

Crystal Barricade AND Rune-Sealed Wall Next is this Azorius artifact Wall defender duo

Davriel also uses the perpetually and conjure mechanics, further solidifying him as a planeswalker not meant for paper in fact, Historic Horizons will have a "digital-first" Planeswalker for every color, each with a themed pack of their own

There are potential Standard applications too

When he is not complaining about an unfair removal, you can find him fiercely defending his Delver of Secrets at a pauper table