Render a graphical pattern where each pixel is colored by the value of 'x xor y' from an arbitrary color table.

/*REXX program renders a  graphical pattern  by  coloring  each pixel   with   x XOR y  */
/*─────────────────────────────────────────  from an arbitrary constructed color table. */
rows= 2                                          /*the number of rows in the color table*/
cols= 5                                          /* "     "    " cols  "  "    "     "  */
        do row  =0  for rows*3                   /*construct a color table, size  25x50.*/
          do col=0  for cols*3
                              $= (row+col) // 255
          @.row.col= x2b( d2x($+0, 2) )  ||,     /*ensure $ is converted──►2 hex nibbles*/
                     x2b( d2x($+1, 2) )  ||,
                     x2b( d2x($+2, 2) )
          end   /*col*/                          /* [↑]  construct a three-byte pixel.  */
        end     /*row*/
 
        do   x=0  for cols                       /*create a graphical pattern with XORs.*/
          do y=0  for rows
          @.x.y= bitxor(@.x, @.y)                /*renders 3 bytes (a pixel) at a time. */
          end   /*y*/
        end     /*x*/                            /*stick a fork in it,  we're all done. */