TensorBoard Images' tab shows black or gray squares only

Question

So I was running TensorBoard on a google colab's notebook and when I was checking the Images' tab, all I got back were some black or gray colored squares for every layer: Why am I getting these sort of images and not proper ones? The only thing I can think of, is the fact I'm using TensorBoard on Google colab through this method which could be messing something up.

This is the code I used:

tensorboard = TensorBoard(
    log_dir=r'./logs/{}'.format('main_model'),
    write_graph=True,
    write_grads=True,
    histogram_freq=1,
    write_images=True,
)