I have wrong colors in software rendering. Most likely it is byteorder problem. Better looks screen shot. I tried nv and nouveau driver, both have same drawing. Related bugs:
https://bugs.launchpad.net/ubuntu/+source/mesa/+bug/366755
http://bugs.freedesktop.org/show_bug.cgi?id=22017
My software:
Package: libgl1-mesa-glx
Version: 7.4.4-1
Versions of packages libgl1-mesa-glx depends on:
ii  libc6                         2.9-12     GNU C Library: Shared libraries
ii  libdrm2                       2.4.11-1   Userspace interface to kernel DRM 
ii  libx11-6                      2:1.2.1-1  X11 client-side library
ii  libxdamage1                   1:1.1.1-4  X11 damaged region extension libra
ii  libxext6                      2:1.0.4-1  X11 miscellaneous extension librar
ii  libxfixes3                    1:4.0.3-2  X11 miscellaneous 'fixes' extensio
ii  libxxf86vm1                   1:1.0.2-1  X11 XFree86 video mode extension l

Versions of packages libgl1-mesa-glx recommends:
ii  libgl1-mesa-dri               7.4.4-1    A free implementation of the OpenG

andrey@power-debian:~$ glxinfo 
name of display: :0.0
display: :0  screen: 0
direct rendering: Yes
server glx vendor string: SGI
server glx version string: 1.2
server glx extensions:
    GLX_ARB_multisample, GLX_EXT_visual_info, GLX_EXT_visual_rating, 
    GLX_EXT_import_context, GLX_EXT_texture_from_pixmap, GLX_OML_swap_method, 
    GLX_SGI_make_current_read, GLX_SGIS_multisample, GLX_SGIX_hyperpipe, 
    GLX_SGIX_swap_barrier, GLX_SGIX_fbconfig, GLX_MESA_copy_sub_buffer
client glx vendor string: SGI
client glx version string: 1.4
client glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_allocate_memory, 
    GLX_MESA_copy_sub_buffer, GLX_MESA_swap_control, 
    GLX_MESA_swap_frame_usage, GLX_OML_swap_method, GLX_OML_sync_control, 
    GLX_SGI_make_current_read, GLX_SGI_swap_control, GLX_SGI_video_sync, 
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGIX_visual_select_group, GLX_EXT_texture_from_pixmap
GLX version: 1.2
GLX extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_OML_swap_method, 
    GLX_SGIS_multisample, GLX_SGIX_fbconfig
OpenGL vendor string: Mesa Project
OpenGL renderer string: Software Rasterizer
OpenGL version string: 2.1 Mesa 7.4.4
OpenGL shading language version string: 1.20

My hardware:
0000:00:10.0 VGA compatible controller: nVidia Corporation NV17 [GeForce4 MX 420] (rev a3) (prog-if 00 [VGA controller])
	Subsystem: nVidia Corporation Device 0008
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz+ UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 248 (1250ns min, 250ns max)
	Interrupt: pin A routed to IRQ 48
	Region 0: Memory at 91000000 (32-bit, non-prefetchable) [size=16M]
	Region 1: Memory at 98000000 (32-bit, prefetchable) [size=128M]
	Region 2: Memory at f1000000 (32-bit, prefetchable) [size=512K]
	Expansion ROM at 90000000 [disabled] [size=128K]
	Capabilities: [60] Power Management version 2
		Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
		Status: D0 PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [44] AGP version 2.0
		Status: RQ=32 Iso- ArqSz=0 Cal=0 SBA- ITACoh- GART64- HTrans- 64bit- FW+ AGP3- Rate=x1,x2,x4
		Command: RQ=1 ArqSz=0 Cal=0 SBA- AGP- GART64- 64bit- FW- Rate=<none>