A mandala is used in Buddhism as an aid to meditation. They meditate on the image until they are saturated by it. They believe that you can merge with the deity by meditating on the mandala.
Focusing on mandalas is a spiritual practice where you merge with “deities”–this practice opens the door to demons.
The thing is, how is the devil going to get Christians to meditate on mandalas?
No Christian would put one in their house and sit and stare at it for an hour, chanting the sacred word!
But if the enemy can get a Christian to stare at a mandala because they are coloring it, he can have them absentmindedly focus their attention on the image and they will unknowingly open up their subconscious to this image in almost the same way.
A mandala is a key tool to practicing a religious ritual, and it opens people up to trances. When you think about how our brains zone out when we color anyways, this makes it even more interesting.
We need to be aware of what these images are, because they are not just pretty shapes and designs.