In form design view color-related properties in Kexi forms do not support transparency. Originally reported at http://forum.kde.org/viewtopic.php?f=221&t=108406 Development note: Custom colors can be picked but KColorCombo is limitated as it opens dialog without transparency support: http://api.kde.org/4.9-api/kdelibs-apidocs/kdeui/html/classKColorCombo.html Quick solution will be to add transparency properties with values 0..255 but it would be deviation from the .ui format. So better use KColorCells showing palette and transparency slider.
KColorButton supports alpha channel. I did not add it to KColorCombo, because my impression was that it is used as a quick "pen color" style selector, not something designers need. If you need alpha channel support in KColorButton, please add an entry for kdelibs/kdeui.
Of course I meant "if you need alpha channel support in KColorCombo..."
@Christoph I'll add the entry even if I need to have support for existing KDE installations and anyway will be migrating to KColorCells-based solution.
@Christoph done https://bugs.kde.org/show_bug.cgi?id=309290
*** Bug 333550 has been marked as a duplicate of this bug. ***