Add swimlane color contrast to Default theme

What is the challenge?

There is not enough visual contrast between the swimlane color and the row header color in the Default theme for pivot reports. This makes it difficult to distinguish the swimlane grouping from the row labels at a glance.

What is the impact?

Reduced contrast affects the readability and scanability of pivot reports, especially when they include many rows or are reviewed in presentations. Users must spend more time interpreting the report structure, which can lead to confusion about which information belongs to a swimlane versus a row header. This also creates an accessibility concern for users with low vision or color-contrast sensitivities.

Describe your idea.

Update the Default pivot-report theme so the swimlane background uses a darker shade of blue. The new color should sit visually between the existing row-header and column-header colors, creating a clear hierarchy while preserving the overall theme. This change should improve structural clarity, readability, and accessibility without requiring users to customize report styling.