The clear command is doing a terminal reset.
The default foreground for any wyse terminal is the high intensity of the base color. It's kind of a side effect of the fact that a real wyse terminal is not a color terminal (and has green on a black background and not black on white like the telnet pro windows style default).
What I personally do is to change to a white on black color scheme (you could also try something like cyan on black, green on black, etc).
Since you said you didn't see the behavior in older versions I assume you were using 4.3 or the classic client which starts with a black background.
You could try this profile to revert to the old classic client colors:
ftp://ftp.jriver.com/pub/TECH.SUPPORT/profiles/wyse60.cfgJust import it under profiles. Make sure the terminal type is set properly afterward and use the host edit box to change to that profile from the default.
You could also just change the default profile yourself with the profile editor. Make sure that you change all of the colors to something compatible not just the normal foreground and normal background.