Altec 17's:

Check here:

http://www.lansingheritage.org/html/altec/altec.htm

As you can see (via the link) 18" woofers were not used and the 17/18
models used single coaxial drivers.

Even the VOT used a 15" woofer.

Models 14, 15 & 19 used woofer/horn tweeter combos.

If you are talking about the Altec 18 two way speaker with a horn at the top
and an 18" woofer in a separate cabinet at the bottom, it is a fabulous
speaker for rock. I had heard it in a friend's home in the late '70s driven by a
211 SET amp that I built (see my system). The amp had only 19W output per
channel but it rocked and shake the whole house. Also, its horn was the first
one I had heard that didn't sound like horn - a major accomplishment at that
time.

I have never seen one with two colors. Maybe it had been refinished
afterwards. I would be interested to see some pictures. Can you post some
here?