There are several ways you can customize  your calendar. The easiest is using views.
1. Go to your team site where your calendar  resides
2. Click "documents and lists" at the top nav
3. Scroll down and find the web part you'd like to modify (i.e. calendar)
4. Under "Actions" on the left hand navigation click "Modify Settings and columns"
5. Bottom of the page under "views" click "create a new view"
From here a wizard will walk you thought the rest. Play around with it and know that these same steps apply to any list you create.

If you'd like to change  the appearance, layout and links from the calendar -
1. Locate the web part you'd like to change the appearance of (links, calendar etc)
2. Right side of the web part tool bar is a down arrow. Click it
3. Modify Shared Web Part
4. You can select the view  you created above, the tools bar etc. One of these groups is appearance. It is here you can change the pixel height and width for this part.
5. Once selected click "ok"
Play around with this to see what each of the selections perform.

To my knowledge the only way to change the color of the calendar is through your Cascading Style Sheets (ows.css) or simply change the theme.

ows.css is applied to all WSS sites with canned styles and formatting issues. Make sure that you know what parameters you are changing. The following link is excellent in letting you know what parameters impact what section. sharepointcustomization.com/.../wss_cssguide.htm Do a find for "calendar" to get the applicable sections.

Keep in mind the beauty of CSS is you make one change  and all code using that parameter is updated. This is a beautiful thing but can also be harmful if not correctly performed.