I'm not sure if it is a bug, or by design but:
Borders are not coloured, i made some changes to Toolkit.c:
Added "attron(attr);" at line 374, and an "attroff(attr);" at line 417 to set the color attributes which are set with "if (colors_started) attr = COLOR_PAIR(colorpair_);" in the function Java_charva_awt_Toolkit_blankBoxNative
After i recompiled the Toolkit.c borders are now coloured.