I should have read the kernel driver sources carefully:

static int pxa_cam_WCAM_VIDIOCSNIGHTMODE(p_camera_context_t cam_ctx, void * param)
{
    struct {u32 mode, maxexpotime; } cam_mode;
    u32 maxexpotime;
...

Picture. Now with colors. Will write a detailed description on how to use A1200 driver interface later.

:)