This is a great shot and successfully completes what was asked of you for this assignment. You’ve narrowed your color palette down to 3 main colors and a 1 color highlight. Likewise, your earthy background colors really help your flower stand out. Not only that, but your depth of field helps further isolate your flower petal from the rest of the shot.
The element of this photograph I like most (and it might have been unintentional) is the graininess of the shot. You have very nice soft lighting and really good exposure levels. You probably took this shot on an overcast day or early morning or close to the evening. The reason for the graininess has to do with your camera’s technical capabilities. Many digital cameras don’t fare very well in low light conditions. This graininess (known as pixilation in digital cameras) is hard to avoid in low lighting situations.
If you don’t’ like the graininess, you can make it more subtle by changing your digital ISO speed. The lower the number the less grainy it will be. For example an ISO of 50 or 100 will be less grainy than an ISO of 800. As a general rule of thumb try to use a lower ISO if the light permits you to do so. This will help you get the crispest picture possible (also helps when enlarging your prints). You can usually find this setting under your menu options in your camera.
However, as I mentioned, I like the pixilation in this picture because it provides it with an almost atmospheric quality. While pixilation usually looks terrible when enlarged, in this picture it’s forgivable because of the general composition of the shot.
My only other recommendation would be to be careful of your object positioning. Try to play around with your composition to ensure your objects abide by the rule of thirds. A more informal balance helps gives photographs a more dramatic look.
But overall… A great photograph! Keep up the good work.