I started with the same 1/4 soap 3/4 water solution but it turned out too messy (see the red one on the left).
Later on, I just mixed 10 ml. of liquid soap with 1 ml. of disperse dyes, in my bubble cup with cover, and that worked really well, see right and a few of my other results:
The more dye I used, the better they got, look at theses final ones: