I had opportunity to jump into it just the night before deadline... So I had just one adventurous attempt.
Here it is:
My inspiration was idea of rainbow colored zebra pattern and I used black, white, and rainbow colors in my soap:
Smallest tubes was poured with all range of rainbow colors. Big ones with black, white, and some rainbow leftovers. And straws was filled just with contrast colors. After pouring was done:
After removing big tubes:
Then smaller tubes was out:
And more pictures after final cut. And I wish to have more time for few more attempts in this technique: