I will gladly answer your questions.
Regarding the analyze, you would like to use the force that is needed in order to show that your project serves it's purposes. For example, since you're talking about a curtain then it will not require a lot of weight hence you could analyze it with low force which will be enough for your project.
For the materials, since curtains are supposed to be light you will want the whole system to be lightweight and yet durable (as well as you can also use a material that is against corrosion).
An aluminum alloy material would be a good idea for the project, its sturdy and durable and it is rather lightweight while its also cheap which is something to consider when making a product that is used in every house and office nowadays. You want it to be good, but you do not want the quality to cost too much or else it will not serve it's purpose.
Colors in SolidWorks don't matter, you can use any color or multiple colors to demonstrate a real look of a curtain in the appearances edit, easy to do, does not affect it and adds a pleasant look to the eyes.