Root health

Should healthy roots always be completely white in color?
Are there any types of growth that is beneficial to a root AND that is VISIBLE TO THE NAKED EYE?
Are there any bugs that live in/on roots that are beneficial to root health?

for hydro/aquaponics roots should be white, when they get dark in color in that type of setup then nutrient uptake will suffer

there should be no visible bugs in hydro/aqua because they are feeding on roots or nutrients and will soon overrun things (i use gammarus "shrimp" in organic systems to help break down nutrients, but they stay out of the deep water culture area)