There are at least eight permanents of any particular color on the battlefield.
({2} magic symbol) ({G} magic symbol) available.
Steps
Deal combat damage using Rith.
Rith triggers, causing you to pay ({2} magic symbol) ({G} magic symbol) to create at least eight 1/1 Saproling creature tokens.
Move to your postcombat main phase.
Activate Utopia Mycon's second ability five times by sacrificing five Saprolings, adding ({3} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Activate Aggravated Assault by paying ({3} magic symbol) ({R} magic symbol) ({R} magic symbol) , untapping all creatures you control and causing you to get an additional combat and main phase after this one.
Move to your next combat phase, and deal combat damage using Rith.
Rith triggers, holding priority, activate Utopia Mycon's second ability three times by sacrificing three Saprolings, adding ({2} magic symbol) ({G} magic symbol) .
Resolve the Rith ability, causing you to pay ({2} magic symbol) ({G} magic symbol) to create at least eight 1/1 Saproling creature tokens.
Repeat from step 3.
If there are at least nine permanents of any particular color on the battlefield, this combo will net infinite creature tokens and colored mana.