You need to llok up the bit values of the field atribute byte which preceeds each display field sent to a 5250 emulation.
Of the available 8 bits, each does a different job. When first written, the protocol had functionality such as high inensity (bold) underline, character separators. When colour was invented, the same bits used for these attributes became used for colours.
The net effect is that some combinations don’t work. for example, the old bit for ‘bold’ may have become the bit which indoicates (to a colour terminal) – display in Black (or whatever)
Somewhere – in an ‘old’ paper manual, I have the bit settings laid out – used to be in a published manual – try the DDS Display files manaal
I posted a REXX routine here a couple of days ago that generates all hex values – run it and you’ll see what’s possible
(I’ve no idea how to do a full text search of this site… )