Any corundum without trace elements is colorless. Corundum with trace chemical impurities makes the gems we know. Chromium gives the red to rubies, sapphire has iron and titanium, you can get other colors using vanadium or different ratios. Gems are neat.
The latest version of iOS changes the words if you have spellcheck on. I think it underlines the misspelled words if you have spellcheck off.