I am turning a red oak bowl and have several cracks that have developed.
What is the best way to repair this?

You can use the two part epoxies available at most hardware stores and home
centers. You can color these with artist's acrylic (it does not take much) or
you can add powdered stone ( eg turquoise, malachite, lapis) or brass (swarf
from key grinding, usually free from people who grind keys). As an alternate,
pack the crack with the stone or whateve and drip on thin CA glue. CA stains
some woods,(I don't know about red oak), test on scrap and if it stains, seal
the area around the crack with Deft or a similar product befor you inlay the
crack

Kip Powers
Rogers, AR