Re: Is there a difference between white and high intensity?

> Yes, there is a difference between plain white and high intensity white.

Actually, no there isn't, at least in standard 5250 data stream
attributes. There are InfoWindow II extended attributes that allow for
more than one shade of each color, and for at least some attributes to be
controlled independently of color, and attribute changes that don't take
up screen positions, but they're rather poorly documented (i.e., I've
never once seen any documentation on how to use them, or even anything
that would tell me how to implement them in an emulator).

For basic 5250 attributes, green is synonymous with normal, white is
synonymous with high intensity, red is synonymous with (monochrome) blink,
red blink is synonymous with (monochrome) high intensity blink, cyan
(listed in documentation as turquoise) is synonymous with normal
column-separated, yellow with high intensity column-separated, pink with
normal column-separated blink, and blue with high intensity
column-separated blink.

Display files (and presumably panel groups and other UIM constructs)
recognize whether they're transmitting to a color or monochrome device,
and can store color separately from monochrome attributes, so that
specifying a field as "blue" will not cause it to come up as
column-separated high-intensity blink on a monochrome screen; if, however,
you specify those monochrome attributes without also specifying a color
for the field, it will come up blue on a color terminal.

That's also why, with any color terminals prior to the InfoWindow II
series, anything that comes up in cyan or yellow also comes up
column-separated. (This can be suppressed in setup on 3487s, 3488s, and
3489s.)

I tried a variation of your program, simply sending the message as a
program message, to the regular message line (on the PROGRAM menu). On a
color emulation session, the colors came up as expected, but on the
3477-FA (amber monochrome) that normally lives in the computer cage, but
is standing in for my 3487-HC at the moment, the message came up all
high-intensity, with little white blocks where the attribute changes would
be. That suggests that, at least if the system handles messages, attribute
changes within them are unsupported. Even if that's not the issue in your
case, it's entirely possible that the system is fighting you on
attributes.