CSP inline-style error when hovering over the donut chart tooltip

# CSP inline-style error when hovering over the donut chart tooltip

## Description
When hovering over the donut chart, the tooltip appears, but it triggers a CSP violation due to inline styles.

## Steps to Reproduce
1. Render a donut chart with tooltips enabled.
2. Ensure CSP settings prohibit `style-src 'self' 'nonce-123456' https:; ` styles.
3. Hover over the chart to display the tooltip.
4. Check the browser console for CSP errors.

## Expected Behavior
The tooltip should be displayed without causing CSP violations.

## Actual Behavior
The browser console reports a CSP violation related to `style="background-color: ..."`.

## Possible Cause
After reviewing the source code, I found that inline styles are applied to the tooltip using `style="background-color: ..."`, which is blocked by CSP.

## Suggested Fix
Consider using CSS classes or a safer approach to apply styles instead of inline styles.

## Environment
- **Library/Framework:** [Specify the version]
- **Browser:** [Specify browser & version]
- **CSP Settings:** `style-src 'self';` (or other restrictions in place)

Would appreciate any suggestions or fixes regarding this issue. Thanks!