A combo that gives infinite turns without any colour support needed is Prototype Portal + Ugin's Nexus + any sac out let that lets you sacrifice your copies of the Nexus.
You might want to reread Ugin's Nexus they thought of this stuff when that card was designed.
You might want to reread Ugin's Nexus they thought of this stuff when that card was designed.
You can also plug Scepter into most Karn, Silver Golem & Voltaic Construct combos to give you turns after you get mana off of a rock that taps for 3.