I have been casting for a number of years now and have more casting equipment than turning equipment 
(Though dont tell the Mrs.....)
Agree with most of the above, Clear Cast is a great resin BUT as has been said it goes soft during the sanding process, I use it for Picture Pens as it doesn't mess with the picture (Paper & Ink) where some others love to eat it during the casting process.
Also experiment with leaving the resin for a little while (watch the temp) as you will get much better colour deffinition and they won't bleed into each other (as per your pictures above).
Some of Mine....
These were all Pictures then Clear Cast
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Have Fun 