try it this way:
INT. RAINBOW STAR GIF 1
&overlay INT. RAINBOW STAR GIF 1_OVERLAY create
&overlay INT. RAINBOW STAR GIF 1_OVERLAY moves to layer 1
&overlay INT. RAINBOW STAR GIF 2_OVERLAY create
&overlay INT. RAINBOW STAR GIF 2_OVERLAY moves to layer 1
&overlay INT. RAINBOW STAR GIF 3_OVERLAY create
&overlay INT. RAINBOW STAR GIF 3_OVERLAY moves to layer 1
&overlay INT. RAINBOW STAR GIF 1_OVERLAY opacity 1 in 0 THEN overlay INT. RAINBOW STAR GIF 1_OVERLAY opacity 1 in 0.5 THEN overlay INT. RAINBOW STAR GIF 3_OVERLAY opacity 0 in 0 THEN overlay INT. RAINBOW STAR GIF 2_OVERLAY opacity 1 in 0 THEN overlay INT. RAINBOW STAR GIF 2_OVERLAY opacity 1 in 0.5 THEN overlay INT. RAINBOW STAR GIF 1_OVERLAY opacity 0 in 0 THEN overlay INT. RAINBOW STAR GIF 3_OVERLAY opacity 1 in 0 THEN overlay INT. RAINBOW STAR GIF 3_OVERLAY opacity 1 in 0.5 THEN overlay INT. RAINBOW STAR GIF 2_OVERLAY opacity 0 in 0 loop infinite times