You’re headed in the right direction, but body isn’t specific enough here. There are many layers under / within that need to be considered.
Give this a try (a basic example):
.theme-light {
.workspace-leaf,
.markdown-source-view.mod-cm6,
.markdown-preview-view {
background-color: rgba(255, 0, 0, 0.1);
}
}
I’d check out this excellent topic if you haven’t yet:
