Learn how to create a drop-down list in Excel without or with color using conditional formatting and data validation rules.

Citric acid and vitamin C, or ascorbic acid, are both found in many of the same fruits and vegetables. However, their health effects and commercial uses differ.

Hassler Whitney, The Coloring of Graphs, Annals of Mathematics, Vol. 33, No. 4 (Oct., 1932), pp. 688-718 ...