Yellow and orange would be good colors. You want to use a yellow that is in the same intensity as the orange of the dresses. Burnt Orange sounds subdued. You are not going for a match with your dresses because that gives a very fake look. You want to coordinate the colors to go with the dresses.
There are many flowers that are yellow. Actually, since you are using silk flowers ... you can dye flowers yellow and or orange with fabric dye. So if you can get white silk flowers ... you can get your orange or yellow pretty easily.
Make sure to always wear gloves with using dyes. Follow package directions exactly for rinsing so the colors don't rub off.
Use nice silk flowers. If they look nice to you up close ... they should photograph well. Personally I think real flowers are less expensive than nice silks. But they are more difficult to use than silks and if you have allergies ... can be a real problem.
Since the wedding is at 4 and the reception will be after 5 this means it will be more formal. Anything in the line of a cocktail type dress would be appropriate. If you are going to buy something, get something you will wear again, maybe to another holiday party. Black is always appropriate at this time of day. If you can't find anything you like in a cocktail dress, look for something that you'd wear to church or out for a nice dinner. A skirt and dressy blouse or sweater would be appropriate as well.
Since its Nov. you can wear anything in the jewel tones, Royal Blue, Royal Purple, burgundy any of the deep rich colors, however stay away from red. You don't want to draw attention away from the bride.
When you go dress shopping, tell the sales person what you need the dress for and they will be able to help you. Get something simple and you'll use it again. Dress it up with a necklace and earrings. But above all, be comfortable.
If you are not sure in what season you are getting married here are some ideas that you could try. If it's near fall, think browns, beiges and whites. If it's more towards winter, think winter wonderland with varying shades of blue and white. Any shade of green would be appropriate -- sage, celadon, etc. You could also go with a light blue, and have a "snow and ice" theme -- this is becoming very popular.
You could also choose champagne for your bridesmaids and have floral accents of red and green if you wanted to give a nod to the time of year. You can be as creative as you want with your theme. Colors are wonderfully tied in everywhere with invitations, flowers and favors.
A valentines wedding is always romantic! I would stick with your main colors, with gold or red colored favors to accent the flowers and hurricane lamps (which I do hope you will be lighting with candles!). The other rose color would be white or rich ivory, maybe with a touch of deep green foliage. Red and white are the color symbols of unity. The MOH's red gown would look quite stunning with a bouquet of cream roses, maybe with an accent of red by sprinkling red crystals through the roses. Or a trailing red ribbon. Your flowers could be the opposite (red roses with clear diamante crystals)
Colors like baby blue, baby pink, lavender, lime green and lemon yellow. Actually all these colors would work together; however, I would add at least one more dramatic color, such as a deep pink or fuchsia. You need to create dramatic effect.
I don't have any pictures of these colors; however, the best way to see them is to go to a hobby store that carries silk flowers. This way you can play with the colors to see how they will work together as well as possibly getting other ideas.
Start with the colors you've mentioned and try different "dramatic" colors such as deep purples, blues, yellows to see what you like the best then let your florist know. Also, your florist is a great resource as well for knowing colors, flowers etc.
There's a wonderful magazine, which you can purchase at good book store. It's WEDDING FLOWERS. It comes out once a year and has the flowers grouped in colors as well as wonderful additional ideas for combinations.