Vertebrate blood is one thing that is opaque due to hemoglobin, and it cannot be made transparent. The same is true for the pigmented retina of the eyes. So transparent frogs and fishes still have opaque eyes and blood vessels.

Where pigments like the heme of the blood or the melanin of the skin or the visual pigments of the retina are absent, the opacity is due only to the variable refractive index, which causes light scattering, and in this case the tissue can be made transparent with methods like that described in the article which make the refractive index uniform (i.e. exactly like snow that transitions from opaque to transparent when melting).

They use tartrazine that is a common dye for food, not crushed Doritos. They need a lot of dye to change the internal refraction index and make the meat transparent. So they choose it. From the research article https://pmc.ncbi.nlm.nih.gov/articles/PMC11931656/

> It is a hygroscopic compound with a high solubility in water and minimal reactivity. The European Food Safety Authority (EFSA) has concluded that this molecule exhibits no adverse effects or systemic toxicity at doses up to 2 g per kilogram of body weight (14). As a result, it is widely used as an artificial food dye in products such as flavored chips (for example, Doritos).