> YEL-LOW (2 syllables must be yellow)
> RED (very short word must be red)
> Blue (medium length, ending in OO)
> blaCK (medium length, ending in CK)
>
That right there is so true at least for the top two. I'm fairly certain you're right on the others, in particular BLUE. You could try saying: slew, glue, moo, foo, flew, spew...anything similar and maybe it will take it as I've never tried.