I think this could be solved with a family that is a generic model, face based, rectangular extrusion, a panel. The familiy would have its width and height as instance parameters; so that it can adjust to any rectangular dimensions you might need. The thickness might be by type. For having random colors in the project, create a material parameter in the family. Make it an instance, and apply this material to the extrusion (the panel). Then, in the project, layout your panels on the elevations, and stretch their dimensions with the pull blue arrows. Then select the panels, and change their colors by changing their instance material parameter.

If you need to schedule the panel dimensions and their colors, the parameters mentioned above need to be shared, and the panel family needs to be in a category that can be scheduled, such as Specialty equipment. If the panels need to cover large areas, you might need to go further and create a family that is a row of panels, or a grid of panels, which is a more advanced solution.

Alfredo's method would be very flexible, but also hard to coordinate. And possibly a LOT of work if you have a large building.
Why not use a Curtain Wall with some custom panels?

Create the panels as described above (only then as a Curtain Wall Panel family), also with a type thickness and instance material parameter.
Create a new curtain wall type, without any mullions appointed or any spacing applied.
Place the curtain and use the Place Gridline command to manually place Gridlines. This way the placement is flexible but also dimensionable. When you need segments to be removed, select the gridline and use the Add/Remove Segments command.
Use the custom CW Panels to fill the CW. When you want to change colour simply select the panel you wish to change and apply a different material.

Thank you for the replies.

I am trying the curtain wall option first, as it sounds quite flexible. Then I can refine it as the project continues. I've created a panel family with a visibility parameter to select the colour of the panel, and it seems to bew working quite well so far...

The assigning of colour by grey scale image apparently requires good knowledge of the API, so out of my reach at the moment!

Well, you got 2 different options. The first option requires some time to make some custom families for panels. I do prefer that option, and I know it works very well.

The second option is available immediately since the curtain wall is already a tool that you can use.

Not true. Simply create 5 different materials, each with its own shade of gray, which you can set up with precision if you use RGB settings. Then, simply apply these materials to your panels.

Check out Zach Krohn's blog (Buildz). He created/got his hands on an addon which can do this. Spended a few blogposts on them, so you should be just fine!

actually, Alf's method is super easy to coordinate and "install" like on this project

The curtain wall panel option is working well so far and will get me through the trial and error, and many changes of the design phase of the project, but I will have to re-visit the walls when we progress to construction information. I think Alfredo's method may be more schedule friendly?

Here is a link to the (API) assign colour with grey scale image method for anyone else interested:

http://buildz.blogspot.com/2009/12/a...el-plugin.html

I haven't tried it yet but will give it a go when I have some free time.

Thank you again to all for your advice!

But what if there are a lot of design changes? How do you keep the panels aligned then?
As for the schedules: you can simply schedule the CW panels, so I see no problem in that (just use Shared Parameters for all the stuff you need scheduled, like the material and/or thickness).

I agree with mdradvies. I'm working on a project which also contains a facade made out of different coloured panels and used the curtain panel method and it works ok so far. Especially when you have a regular panel pattern. When the panel pattern (the curtain wall grid) becomes inregular I think things would change.