Activated abilities may be used any time you have priority unless another effect or it says otherwise. So yes you may activate it on any players turn so long as you can pay the costs.
A cards colors are determined by the casting cost or color indicator unless otherwise modified. Devoid cards are colorless and cant be found with Sunforger.
Alternate costs cant be used because the sunforger is casting it for the alternate cost of "not paying its mana cost". You can pay for additional costs like kicker and escalate however if able.
A cards colors are determined by the casting cost or color indicator unless otherwise modified. Devoid cards are colorless and cant be found with Sunforger.
Alternate costs cant be used because the sunforger is casting it for the alternate cost of "not paying its mana cost". You can pay for additional costs like kicker and escalate however if able.