So here's the trick.

You use 99% transparency and two Refract nodes. One Refract node uses an IOR of 1.0, which means it does not bend the light. Basically, it gives us information about what the transparency effect is generating for the material. If we subtract this from the output, using the right amount as a multiplier, we can exactly cancel out the data coming from the transparency effect.

So I take my Refract node with the data I want (colored blue and an IOR of 1.3) and I subtract the other Refract node (untinted and no bend). This produces a color which is the difference between what I want and what I'm getting from transparency.

The only remaining problem is that the transparency effect is giving very little weight to the color I want. In fact, I only get 1% of that. So I multiply it with 99. This gives me 99 times the color I want minus 99 times the color I'm getting.

The transparency effect then multiplies that with .01, yielding .99 times what I want minus .99 times the transparency color. Since the transparency is 99% or .99 times the color behind the prop, I exactly cancel the effect.

I'm still getting a 1% shadow but that is so weak you can't see it. And I'm also only getting 99% of the color I want, but that is so close to the color I want it works fine.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)