For the most success, the color channel needs to be black. If you want colored glass, change the transparency channel to a a color instead of a value. Carrara adds the color channel, transparency channel and shininess channel together which creates the glowing effect you describe - especially when the total value of all three exceeds 300%.

So, that's why it's best to put black in the color channel, and then use a color in the transparency channel - it keeps the total value below the "glowing" threshold.

Transparent objects inside of transparent objects is not a problem. For liquid, the sides of the liquid object should not intersect the glass, however - that will produce weird effects.

Translucency is good for opaque liquids like milk where a little light passes through but you can't see through it. Translucency is not a good addition to clear liquids.