I am using MacOS and a dark theme. Running tkcon defaults to a very dark background for me, but the font colors are also dark and are hard to see.
This is particularly bad for the input lines, which end up being black-on-slightly-lighter-black. (Dark blue on black is also not great).
Workaround
Put set ::tkcon::COLOR(bg) #DDDDEE in ~/.tkconrc. You must restart tkcon for this to take effect (this is unlike how most other options work).
Desired behavior
Ideally, tkcon would properly adjust to a dark theme and used a lighter colors for fonts as part of the dark theme automatically.