Not Vanill Milkshake but Chocolate Milkshake Lube

[Swivelhart]

I pulled apart my stringer today and replaced the water pump. While I had the lower unit off I noticed down by the swivel bearing there was some water. I picked it up and turned the outdrive upside down and saw a bunch of chocolate colored water pour out. It was viscous like gear lube...but why brown. I do not have the heavy duty lower unit that was optional for my boat in 66 but rather the standard group outdrive which has a very long driveshaft that goes deep into the lower unit. Any ideas why it is chocolate colored instead of vanilla colored?

Everything seems to fit very well on this old drive and none of the parts seem worn. I did notice some chunks of rusty stuff in the exuast housing.