slag wrote:

Does anyone make a multicolor mechanical pencil? Like the old 4 color
bic pens in a pencil?

I tried to arrange one of these by asking if I could buy a couple more
of the little pencil mechanisms they make for the inside of a Rotring
600 tri-pen, because they seem to be made to fit into the same size
opening as the little pen refills. The store here told me they weren't
available separately at that time - but maybe you could get them somehow.

I don't know, but I assume there are other multi-pen-&-pencil gadgets
that are built in a similar way.

Note: All the coloured leads I've seen are 0.7 or bigger - I think the
0.5 and smaller sizes break too easily and so are not made.

David