Bitfields for TI Professional PC screen attribute:
Bit(s)	Description	)
 7	alternate character set (requires user-supplied ROM)
 6	blink
 5	underline
 4	reverse video
 3	character enable
 2	green (color) or 58% intensity (gray-scale)
 1	red (color)  or 27.5% intensity
 0	blue (color) or 14.5% intensity