This is the only card in the deck that shows 'full frontal nudity', and it is directly in the center of the card. The two imps' line of sight is aimed straight at the red tip of the penis.
Let's look at the colour symbolism in this card. The basic colour meanings are listed on pages 63-64 of Ben-Dov's book, The Open Reading. I'm going to try to apply them to Le Diable...
Starting from the bottom, a layer of black. The foundation of the Devil card is dark depths, dark layers of the soul. The Devil either stands on or hovers slightly above (I see him as standing on) a platform made of red then green -- passions plus nature -- so he emerges from our dark subconscious passions and natural desires. The Devil's body of legs and torso is pale blue, which Ben-Dov says symbolises 'clarity, transparency, a combination of matter and spirituality, coldness or detachment.' The body is somewhat neutral, then, with the exception of the red around the breasts and pelvis and tip of the penis, the 'passion zones'. Then notice that the face, arms and hands, and the pubis, testicles and penis are the beige 'flesh colour' used in the deck. The face, hands and genitals are the way we make connections with other human beings and interact with our environment. Communication and the work we do for survival comes from the head, face, arms, and hands, and a profound and intimate means of interaction and bonding as well as getting of more human beings to join in this social congress comes from the genitals. Ben-Dov adds that the flesh tone symbolises 'something which is part of the querent's identity or personality'. It is surely the case that much of our identity lies the work of our hands, the way we interact with others (faces), and our gender identity/sexuality. The imps are also flesh coloured, and their tethers are flesh coloured -- are they are our natural children? Our habits? The products of our 'natural' activities? They don't look miserable...so the ties that bind them are not trapping them, and they're not being tormented. They're just attached. Why do they have their hands behind their backs? That's an interesting question!
The red continues as the inner cap beneath the Devil's crown, and the tip of the flaming torch. Notice the torch is green and red -- nature and passion. The 'temptations' of the Devil and the foundation he stands on are our very natures and drives. Notice he's got a green collar, so his face is framed by red and green -- and if his face is the centre of communication, then all his communications are framed in the context of nature and passion. Yep. (Wow, I'm on a roll).
The colour yellow is said to represent material success and plenty, the element earth, 'intelligence applied to practical needs' and 'a warm and optimistic feeling'! The Devil and his imps are crowned with yellow, the Devil's platform has a halo of yellow, and his wings are yellow. Of course, the Devil's playground is material things and earthly pleasures. Why do you think his wings are yellow? What's it saying about wealth, material things, the pleasures of this world, and the Devil?
The Devil card contains a paradox: 'This is the inherent paradox of desire: acting on it can be perceived as liberation from inhibiting norms, but also as a bondage-like addiction to pleasure and satisfaction.' We can get addicted to and become enslaved to fulfilling all these natural passions and drives.
The Devil card is not about Satan. It's about us.