Hello Bloomer!
Yes... Summer sales are GREAT!
Sale Sale Sale! Look out for the 40% off coupon from Michaels as well.
Theme:
We use lots of dried flower petals for our wedding (cutting cost on the flower). The invitation that we picked got some purple-pressed-petals on the paper and we used lots of dried flower on our enterpiece for the sit-down reception. We used a floral-pattern-stamp on all of the prints related to our wedding: envelope for invitations and thank you cards, the card displaying the table name (instead of table number for the sit-down reception), the menu/guest names thingie... (I made this triangular prism without the top and bottom, where one side is the menu of the buffet, one side is just a poem and the names of the wedding party, and the 3rd side was the names of all of the guests at each table)
For us... it was just trying to keep all of our print job parallel as we did everything ourselves and we didn't want them to look tooo "home-made"... that's why we came up the idea of a theme. Here is a site for some idea :
http://www.wedthemes.com/ I wanted a beach theme to begin with, but beach theme in November doesn't seems to be nice :P Items that you would try to work on (if you have a theme) would be the ring pillow, the candle holders, the flower girl basket, cake top, pen for signing the license, guest book, centrepiece... etc.
Colour:
For our colour, we had purple and ivory... (although, you see a lot of red in my photos... that's more because I was an asian bride). We used the theme colour on all of our print jobs, the flower [bridesmaids' Bouquets, all of the corsages (for mothers and VIPs), boutonniere (for groom's men and fathers and VIPs) + flower on the cake, and 1 flower arrangement for the sign-in area], the bridesmaids + flower girl dresses, the tux for the guys (you can pick your colour even when you rent the tux), the cake. We also picked up some chain light (those summer outdoor floral chain-lights from Ikea in purple and ivory)
It would be nice if my dresses, except the wedding dress, to be in purple.. but again... I was an asian bride... so red was the colour that we went with. For us, the idea of having a theme and the main colours is just to try to make the wedding to look "less-home-made" and it looks like the goal was achieved :P
For spring wedding, you can consider pastel colours. I would suggest either to stick with 1 colour and go with different shade or to stick with max 3 different colours (otherwise, it might look too busy).
I am now planning for a yellow-red-orange wedding in the summer, I picked up some orange candle at Canadian tire for 99 cents for a pack of 15 candles. It is just awesome; once you have a theme colour, you can really get some good deals when you start looking.