I was fiddling around with the code a little and found this gives great results, and it's random every time you turn the Odyssey2 on:
mov r0,#lettercolor
movx a,@r0
add a,#8
movx @r0,a
mov R1,#lettercolor
mov R0,#03Eh
mov a,t
anl a,#0F8h
movx @R1,a
I put this in a call routine when the sprite color needs to be changed.
The "lettercolor" is actually a sprite. The sprites are letters. I got bored of the standard ones so I made a couple of new ones. They're lowercase this time. I thought the Odyssey 2 had an RNG, the t (for timer) function. Or am I wrong?