Normally, this would be done with a single installation and using categories (one for each of your pieces of equipment). Then using the $showCat filter, you could have as many pages as categories, each only showing a single category. Each category is assigned a color, so you could do the color coding that way.
Events are entered via the Event Manager, which does require login (and has a limit of 20 users), but once you gain access, you access everything. There is no permission scheme in v6 (v7 will have that). I would suggest that you create a custom event entry form, so that you can decide whether events are posted immediately or forwarded to an administrator of some kind to enter in the database.
Bandwidth figures are impossible to figure out, as it entirely depends on how much content you will feed in the database.
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