To apply single-color/classic conditional formatting,
1. Click on the Format menu.
2. Select the Conditional Formatting option.
3. Click on Classic from the drop down.
4. Once the Conditional Formatting window appears, select the range of cells you want the conditional formatting to be applied to.
5. You can format the cells based on cell value, text, date, cell content or a formula.
6. You can specify how you want the cells to be formatted, by customizing the color, font style, font size etc.,