Conditionally populate the color on ALV Report Display

*&---------------------------------------------------------------------*
*& Report  YTEST01
*&
*&---------------------------------------------------------------------*
*&
*&
*&---------------------------------------------------------------------*

REPORT  YTEST01 no standard page heading
                line-count 255
                line-size 255.
TYPE-POOLS: slis.

DATA: BEGIN OF it_flight OCCURS 0,
       carrid  LIKE sflight-carrid,
       connid   LIKE sflight-connid,
       fldate   LIKE sflight-fldate,
       seatsmax LIKE sflight-seatsmax,
       seatsocc LIKE sflight-seatsocc,
       color(4),   " <---extra field for color
      END OF it_flight.
DATA: it_fieldcat TYPE  slis_t_fieldcat_alv,
      layout TYPE  slis_layout_alv.

CALL FUNCTION 'REUSE_ALV_FIELDCATALOG_MERGE'
  EXPORTING
    i_program_name         = sy-repid
    i_internal_tabname     = 'IT_FLIGHT'
    i_inclname             = sy-repid
  CHANGING
    ct_fieldcat            = it_fieldcat
  EXCEPTIONS
    inconsistent_interface = 1
    program_error          = 2.

SELECT  carrid
       connid
       fldate
       seatsmax
       seatsocc
 FROM sflight
 INTO CORRESPONDING FIELDS OF TABLE it_flight
 UP TO 20 ROWS.
*-conditionally populate the color
LOOP AT it_flight.

  IF it_flight-seatsocc eq 0.
   it_flight-color = 'C600'.
  ENDIF.
  MODIFY  it_flight.
ENDLOOP.
*-Pass the color field information to layout
layout-info_fieldname = 'COLOR'.

CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
  EXPORTING
    i_callback_program = sy-repid
    is_layout          = layout
    it_fieldcat        = it_fieldcat
  TABLES
    t_outtab           = it_flight
  EXCEPTIONS
    program_error      = 1.