Unholy frenzy is red and white because it does damage and buffs you. But there is no upside to Mind Worm.
Mind Worm may not appear to have an upside, but I does. One example of wanting to use Mind Worm on your self is to remove another detrimental attachment (assuming you have three and the earliest attached card is the one you want to remove). Another example, although very specific, is that you are attached with Blind Rage, only 6 health remaining, with 2 unusable attack cards in hand. At that point you would die at the beginning of the next round if you were unable to discard. Mind Worm would allow you to stave of death, even if only momentarily.
While i would be fine with it being all red Lance is correct in the reasoning that there certainly are self cast uses for it.
Additional, in point of fact, Unholy Frenzy is not red and white because it damages and buffs you; but because it is hybrid attack and assist card. It is the card type that determines the color of the card.
I have to agree that I think this is a bug. Although there are cases where Mind Worm might be an assist, they're pretty unlikely. Red/White cards are generally those that do two things, one helpful and one harmful, not cards that have an effect that can sometimes be useful. In that case, we'd have to make Bash a Red/White card too as you can use it to Push allies into useful places.
