To enable another theme, just open Settings > Change theme.
All theme files are located in \bin\ directory of Debotnet and can be viewed as plain text with an editor of your choice.
Just copy one of the following [Theme] sections (or create a new) into a text file, save it as .DESIGN filetype and move it to the above mentioned directory of Debotnet. You're done!
[Theme]
AppBadge=000000
AppBadgeFontColor=ffffff
BackColor=f0eee0
FontColor=000000
FontColorLight=002bf8
NavTopFontColor=002bf8
Search=66e2d5
SearchActive=002bf8
SearchFontColor=000000
NavLeftMenu=fffdc4
NavLeftMenuFontColor=000000
NavMiddleMenu=66e2d5
SearchFontColor=000000
DebugFontColor=002bf8
Divider=fdf9f3
FooterFontColor=000000
Settings=0030b3
SettingsFontColor=ffffff
[Theme]
AppBadge=000000
AppBadgeFontColor=ffffff
BackColor=FCF3E0
FontColor=000000
FontColorLight=6d6d6d
NavTopFontColor=000000
Search=FCF3E0
SearchActive=89857D
SearchFontColor=000000
NavLeftMenu=F3BC52
NavLeftMenuFontColor=000000
NavMiddleMenu=FCF3E0
DebugFontColor=003df8
Settings=FADE92
[Theme]
AppBadge=000000
AppBadgeFontColor=ffffff
BackColor=000000
FontColor=ffffff
FontColorLight=0062af
NavTopFontColor=ffffff
Search=262626
SearchActive=363636
SearchFontColor=ffffff
NavLeftMenu=520c21
NavLeftMenuFontColor=ffffff
NavMiddleMenu=262626
DebugFontColor=ffffff
Divider=000000
FooterFontColor=ffffff
Settings=363636
SettingsFontColor=ffffff
[Theme]
AppBadge=000000
AppBadgeFontColor=ffffff
BackColor=012456
FontColor=ffffff
FontColorLight=dbff00
NavTopFontColor=ffffff
Search=012456
SearchActive=ffffff
SearchFontColor=FFFFFF
NavLeftMenu=012456
NavLeftMenuFontColor=ffffff
NavMiddleMenu=012456
SearchFontColor=000000
DebugFontColor=dbff00
FooterFontColor=ffffff
Settings=EDEBE9
[Theme]
AppBadge=000000
AppBadgeFontColor=30DCFC
BackColor=0402AC
FontColor=30DCFC
FontColorLight=FCFE64
NavTopFontColor=45FEFC
Search=0F0F0F
SearchActive=30DCFC
SearchFontColor=30DCFC
NavLeftMenu=0402AC
NavLeftMenuFontColor=45FEFC
NavMiddleMenu=0F0F0F
SearchFontColor=000000
DebugFontColor=FCFE54
Divider=54FEFC
Footer=0F0F0F
FooterFontColor=54FEFC
Settings=EDEBE9
[Theme]
AppBadge=000000
AppBadgeFontColor=ffffff
BackColor=1E1E1E
FontColor=ffffff
FontColorLight=979797
NavTopFontColor=ffffff
Search=1e1e1e
SearchActive=1D567C
SearchFontColor=ffffff
NavLeftMenu=252526
NavLeftMenuFontColor=ffffff
NavMiddleMenu=1e1e1e
DebugFontColor=D7BA7D
Footer=68217A
FooterFontColor=ffffff
Settings=252526
SettingsFontColor=ffffff
[Theme]
AppBadge=000000
AppBadgeFontColor=ffffff
BackColor=29235C
FontColor=ffffff
FontColorLight=36A9E1
NavTopFontColor=ffffff
Search=514D72
SearchActive=9391AA
SearchFontColor=36A9E1
NavLeftMenu=A01F80
NavLeftMenuFontColor=ffffff
NavMiddleMenu=29235c
SearchFontColor=000000
DebugFontColor=ffffff
FooterFontColor=ffffff
Settings=602483
SettingsFontColor=ffffff
[Theme]
AppBadge=000000
AppBadgeFontColor=ffffff
BackColor=2f252e
FontColor=e0bf8a
FontColorLight=e45898
NavTopFontColor=e0bf8a
Search=1f8292
SearchActive=40333f
SearchFontColor=e45898
NavLeftMenu=2f252e
NavLeftMenuFontColor=e0bf8a
NavMiddleMenu=2f252e
SearchFontColor=000000
DebugFontColor=206671
Divider=524051
Footer=1f8292
FooterFontColor=000000
Settings=e0c18a
SettingsFontColor=2f252e