Thanks for your comments. 2 and 3 are my favorites. I don't really like like composition of 1 (color) but it does represent what the instructor was asking for - the effect color can have on an image. Number 4 (curves) could have been submitted for shadow, pattern, or curves. Again, your comments are welcome - you can even say number 1 is bad.
Below is another shot of #3 (shadow) taken about 20 minutes earlier in the day. I don't like the shadow running down the center of the picture - it is too symmetrical. I think the shot is better with the shadow line off to the left somewhat.
For Pattern, I took numerous shots with and without the flower, and I also moved the flower to different locations in the frame. Here is also another shot of Pattern (2), taken with the flower closer to the center. I think the shot is best with the flower closer to the corner.