  Multiphase flows are challenging systems to study, not only from a
fundamental point of view, but also from a practical one due to the
difficulties in visualizing phases with similar refraction indices. An
additional challenge arises when the multiphase flow to be observed occurs in
the sub-millimetric range. A common solution in experimental fluid dynamics is
the addition of a color dye for contrast enhancement. However, added dyes can
act as surface-active agents and significantly influence the observed
phenomena. In the recently reported Marangoni bursting phenomenon, where a
binary droplet on top of an oil bath is atomized in thousands of smaller
droplets by Marangoni stresses, visualization is particularly challenging and
the use of color dyes is naturally tempting. In this work, we quantify
experimentally the significant influence of added methyl blue dye, as well as
the obtained contrast enhancement. We find that the reaction of the system to
such an additive is far from trivial and brings an opportunity to learn about
such a complex phenomenon. Additionally, we propose a simple method to analyze
the contrast enhancement as a function of dye concentration, with the aim of
finding the minimum concentration of dye for successful imaging in similar
systems.
