Channeler Initiate and Devoted Druid have at least one +1/+1 counter on them.
Steps
Activate Experiment Kraj using Devoted Druid's second ability by putting a -1/-1 counter on Experiment Kraj, untapping Experiment Kraj.
Activate Experiment Kraj using Channeler Initiate's ability by tapping Experiment Kraj and removing a -1/-1 counter from it, adding one mana of any color.