Hi guys,
I've arranged to marry my long- time girlfriend in December, probably
After Christmas. Can u please advice me on the right colours to use.
It will be a church wedding

Green and red are Christmas colors but that wouldn't look too good for a wedding.
I would say pastel sage and mauve would look nice.

Something like this
ME Prom BT1275 Prom Dress - 2008 Prom Gown

There are loads of really nice dresses on that site
I also like the satin rouge dress.

Choose seasonal flowers you like and base your colors around them. I saw a Christmas wedding where the girls wore green and carried Poinsettias - it looked beautiful. Also, the church was already decorated with Poinsettias from the holidays. This saved the bride and groom some money.

This link guides you through designing a wedding,color themes etc
Choosing Your Wedding Colors: A Guide for Designing Brides

EDIT::
The Meanings of Colors in Weddings

Rich, dark colors like navy blue/emerald green/burgundy/chocolate OR the opposite - white/gold/silver/pale blue

Or simply go with your favorite colors! Its your wedding and there are no "rules" for colors and seasons. Just do what makes you both happy :)

First, find out if your fiancé has something in mind already. She may have been planning this all her life and may know exactly what she wants. Otherwise, for winter, jewel tones can be very elegant - navy, emerald green, burgundy, deep purple, and so on. Some people look washed out in pastels, particularly in the winter, so consider who is in your bridal party and what they look good in.

For economy sake, consider your venue too... if your banquette hall has three colors of table cloths, for example, or if the chairs are upholstered in a particular shade you might want to incorporate that color so you don't have the expense of hiding it or redoing it or paying extra to rent something different.

For men, keep it simple - most men look good in a black or navy suit or tuxedo. I personally think a regular silk tie is a lot more youthful and modern than a bow tie but it's a matter of your personal preference. Before you choose your shirt, find out what shade your fiancé is choosing for her gown. If you wear white and she has a cream color dress, her dress will look dirty next to your shirt!

If I were to have a December wedding it would be ice blue and silver. I bet your fiancé already knows what she wants. Have you asked her?

Red velvet, white poinsettias, and lots of gold and silver.

I would say like a grey like jacket, and a white flower and white shirt and I nice blue tie or something ^_^ something snowy I would say anything with blue and white and maybe a little grey. ^_^ I think that would look wonderful but whatever you choose I'm sure it will be the right decision and you will look fab good luck and congratulations!