In the samples I have seen so far, the ColorJitter is used prior to normalizing.
You can check this out : fastai_imagenet training script 134
    train_tfms = transforms.Compose([
        transforms.RandomResizedCrop(size),
        transforms.RandomHorizontalFlip(),
        transforms.ColorJitter(.4,.4,.4),
        transforms.ToTensor(),
        Lighting(0.1, __imagenet_pca['eigval'], __imagenet_pca['eigvec']),
        normalize,
    ])