Label and style chart elements

The customer churn chart has unlabeled axes and tiny legend text that founders squint at. Label the vertical axis Churn rate (%) and the horizontal axis Month, increase the legend font to 10pt, set the title to Customer churn — trailing 12 months, and make the series colors match the product brand palette (blue for Core, orange for Pro). Deliver the updated chart before Friday's board slides are due.

Before I hand this churn chart to Product and Marketing, make it immediately credible: put the churn rate percentage format on the Y axis with one decimal, bold the series names in the legend, add data labels for the last point only with callouts, and add a short footnote under the chart explaining how churn is calculated. Highlight anything that will make a reviewer hesitate.

Product says the chart colors don't match our brand and Marketing will question the axes formatting. I'm worried they'll think the data is sloppy. I don't know whether the issue is the series color assignment or the palette in the workbook. What should I check first and the exact steps to fix it so both Product and Marketing will sign off quickly?

I spend an hour each reporting cycle restyling charts because stakeholders tweak titles, colors, and labels. This erodes my credibility and delays slides. What standard styling rules should I adopt once and enforce so charts need minimal rework, and how do I get Product and Marketing to accept them as the default?