Macranda & Snails

I am wondering what makes a plant like Red Macranda (sp) turn green.  I
have a 4ft heavily planted tank inside with good and appropriate growth eg
red plants red, green plants green (light 168w) and a bathtub  outside
filled with offcuts of the aquarium plants in pots with sand/laterite.  The
tub is in a shaded position in the yard, but there is a lot of light almost
all year round.

Q.  When I plant the offcuts outside the resultant growth is lush and green
- even for the Macranda.  Is it missing anything?  light? fertilizer?

Also:  I have two Malaysian Trumpet Snails (I think) in my tank for over a
year.  They are big and yellow.  But I am suprised that they have never
laid eggs or had any offspring.  Is there anyway to get them to breed.  I'm
presuming they are unisexed and you don't need a male and female.