Fix invisible disabled menu item text in Subtitle Workshop Classic 6.1.4. The application happens to
use 0xF0F0F0 as the menu background and the inactive caption color to draw disabled menu item text.
In Light theme, the inactive caption color is very close to 0xF0F0F0, thus causing the invisible
text. So use a darker color for inactive captions to avoid this issue. The inactive caption text
color is also adjusted accordingly.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=53575