My first guess would be incorrect config... So lets check that.
Tools > Options > Editor > Display > Color
This page has a tree with colors, (when selecting "ObjectPascal" in the toolbar / selected by default) the first section in that tree is "ObjectPascal" and it has an entry called "Case label".
On my default 3.0 test install, all colors for "case label" are unset => and so they do nothig => and case labels show the underlying normal color.
"Case label" can either be used to apply an attribute otherwise not used (maybe underline, maybe frame), or background color.
Or it can be used to mix colors using the alpha setting.
Or it can be used to change color, but for identifier labels only. For that priorities of string/number color have to be set higher than "Case label".