D2 0.6.3 allows you to make your own and customize existing D2 themes. Here's an example with some random color codes.

See docs

Playground link

Features 🚀

• Themes can be customized via d2-config vars. #1777

Improvements 🧹

• Icons can be added for special objects (sql_table, class, code, markdown, latex). #1774

Bugfixes ⛑️

• Fix importing files that override an existing value with an array. #1762
• Fixes missing unfilled triangle arrowheads when sketch flag is on. #1763
• Fixes a bug where the render target could be incorrect if the target path contains "index". #1764
• Fixes ELK layout with outside labels/icons. #1776
• Fixes a bug where an edge could become disconnected with dagre layout and direction right. #1778