I saw a video of someone analyzing this color spread he brought up many points but i will only focus on one and that is whats written on Zoro's shirt here and the title above.
It is not clear if the word on Zoro's shirt starts with R or B which is clever by Oda since both R or B still makes 2 word that has the same meaning :-
Roisterous - boisterous,
hell-raising, knockabout, rambunctious, raucous, robustious, rollicking, rowdy
Loud and disorderly.
Boisterous - windy,
stormy, boisterous, inclement, tempestuous, rough.
Here is the interesting part of this the title above which symbolizes Luffy "Sea Of Liberty" with the word/s that Oda chose to write on Zoro's shirt. They make a famous Quote :-
„
The boisterous sea of liberty is never without a wave.“ — Thomas Jefferson
What is one of the reasons that causes waves on the Sea? The Sun and the
Moon. The Rowdy Sea of Liberty "Luffy" is never without a wave "Zoro".
Conclusion :-
The Sea of Liberty that Luffy will create will also carry the waves of Zoro in it. With the Defeat of 2 Yonkou that will free the Seas of that power how will Zoro makes his waves i wonder?