Newbie from Italy

Hi everybody!
I am a newbie in keeping tank and I am very interested about this newsgroup.
I am sorry for my english but as you can see, I am an italian exactly from
Rome.
Well, I have a 40 lt. tank of freshwater with a guppy, 3 platys, 6 neons, 1
coridoras and 4 shrimps.
I have some questions for some experts and I hope I can have some easy
suggestions.
1) Is it possible to recognize the gender of neon?
2) what is the right amount of plants needed for a correct setup?
3) how can i emphasize the colour of fishes naturally (I mean not
chemically)?

Thanks a lot and best regards...
MaX (Rome)