With Google, if you have multiple calendars you'll have to create them at Google, not in iCal. You'll have a primary account and can add as many secondary calendars as you need.
With iCal, you'll need to create a CalDav account. To get the secondary calendars to sync to iCal you have to check the "delegates" in the account prefs. Your iCal colors will match the colors you set at Google.
On your iOS devices...to get all the calendars to sync you must use Exchange. Then, with mobile Safari, you'll have to visit m.google.com/sync, log in and add the secondary calendars. The colors won't match as iPhone exchange gives them their own color. CalDav Google syncing on the iPhone gives the correct color, but only the primary calendar.
You can export/import your current calendars within iCal from your original calendars to the new Google ones.