1. Have Snapping Voidcraw and Spawn Gang Commander in play.
2. Tap Snapping Voidcraw for 2 colorless mana
3. Tap a colored land for colored mana
4. Try to activate Spawn Gang Commander. Notice that autotap is using both colorless mana instead of 1 colorless and 1 generic (colored) mana from my pool.
5. Undo the activation from step 4, then re-add the same mana to my pool.
6. Enter full control mode.
7. Activate Spawn Gang Commander and consume 1 Colorless mana from my pool.
8. Try to pay the remaining 1 generic mana cost with colored mana from my pool. No response to the click.
9. Try to pay the 1 remaining generic mana cost with an untapped colored land. Adds mana to pool instead of cost.

I was unable to activate Spawn Gang Commander twice as I intended; the game would only let me spend the 2 colorless mana on a single activation.