Professional models colour cells by what they ARE, not by how they look: blue for a typed input, black for a formula, green for a link to another sheet. That convention is decades old and it exists so anyone opening your file knows instantly which cells they may touch. Cell Styles is how you apply it without hand-formatting — and the real payoff comes later, because editing the style itself updates every cell using it at once. Hand-formatted cells can only be changed one at a time, forever.

1. 1Alt + H, J opens the Styles gallery. **New Cell Style** to define one.
2. 2Name it for its meaning — Input, Formula, Link — and set the format.
3. 3To restyle everything later: right-click the style → **Modify**. Every cell using it updates.

Press the shortcut to play it on a sample sheet.

• Mark inputs blue so nobody types over a calculation.
• Change a model's whole look by editing three styles rather than a thousand cells.
• Hand over a file whose colour coding explains itself.