To use the mode for inference, just load it like a normal stable diffusion pipeline:

from diffusers import StableDiffusionPipeline

model_path = "johnowhitaker/rainbowdiffusion"
pipe = StableDiffusionPipeline.from_pretrained(model_path, torch_dtype=torch.float16)
pipe.to("cuda")

image = pipe(prompt="A cat").images[0]
image