Question

what causes the red color in the red rock visitor center

Answer 1

If you mean the natural red stone around a Red Rock visitor center (for example Sedona or Red Rock Canyon), the color comes from iron oxides — basically "rust" in the rock. Those sandstones started as quartz sand with some iron-bearing minerals. During burial and later exposure, iron in the rock oxidized (Fe2+ → Fe3+) and precipitated as hematite (Fe2O3) or other iron-oxide minerals, staining the grains red. Different iron compounds and amounts give yellows, oranges, browns or reds.

If you meant the visitor center building itself, the red color would simply come from pigments or paint chosen for the exterior.

Tell me which visitor center you mean if you want a site-specific explanation.