You cannot change the sky with this version, but you can change the ambience level through a script. Create a trigger zone, place it near the player. Attach a script to it that controls the ambience for that level. Do this in each level.
;Header
desc = ambience by BenjaminA
;Triggers
:state=0,always:ambience=3,ambiencered=25,ambiencegreen=25,ambienceblue=155:state=0
;End of Script
Change this script for each level and save it as a new file. You need a file for each level.
Or.... you can also use a number of larger triggerzones and change the ambience within the level and have different ambience effects in your level.
This will give you a bright ambience in when the player is in a triggerzone.
;Header
desc = bright ambience by BenjaminA
;Triggers
:state=0,plrwithinzone=1:ambience=95,ambiencered=255,ambiencegreen=255,ambienceblue=255:state=0
;End of Script
This will give you a dark ambience when the player is in a triggerzone
;Header
desc = dark ambience by BenjaminA
;Triggers
:state=0,plrwithinzone=1:ambience=3,ambiencered=96,ambiencegreen=255,ambienceblue=255:state=0
;End of Script
This will give you a more normal ambience again.
;Header
desc = normal ambience by BenjaminA
;Triggers
:state=0,plrwithinzone=1:ambience=28,ambiencered=95,ambiencegreen=255,ambienceblue=255:state=0
;End of Script
You can use a number of these scripts in one level. Attach the scripts and others you've derived from them to triggerzones. When the player steps into the triggerzone the ambience will change. When he's steps into another a triggerzone, the ambiance will change again and so on.
Here are some fun ones:
'Disco' effect
;Header
desc = disco ambience by BenjaminA
;Triggers
:state=0,plrwithinzone=1:ambience=25,ambiencered=255,ambiencegreen=0,ambienceblue=0,timerstart,state=1
:state=1,timergreater=500:state=2
:state=2,plrwithinzone=1:ambience=5,ambiencered=255,ambiencegreen=0,ambienceblue=0,timerstart,state=3
:state=3,timergreater=500:state=4
:state=4,plrwithinzone=1:ambience=35,ambiencered=0,ambiencegreen=255,ambienceblue=0,timerstart,state=5
:state=5,timergreater=500:state=6
:state=6,plrwithinzone=1:ambience=5,ambiencered=0,ambiencegreen=255,ambienceblue=0,timerstart,state=7
:state=7,timergreater=500:state=8
:state=8,plrwithinzone=1:ambience=25,ambiencered=0,ambiencegreen=0,ambienceblue=255,timerstart,state=9
:state=9,timergreater=500:state=10
:state=10,plrwithinzone=1:ambience=5,ambiencered=0,ambiencegreen=0,ambienceblue=255,timerstart,state=11
:state=11,timergreater=500:state=0
;End of Script
Flickering lights:
;Header
desc = flickering ambience by BenjaminA
;Triggers
:state=0,plrwithinzone=1:ambience=25,ambiencered=255,ambiencegreen=255,ambienceblue=255,timerstart,state=1
:state=1,timergreater=900:state=2
:state=2,plrwithinzone=1:ambience=5,ambiencered=255,ambiencegreen=255,ambienceblue=255,timerstart,state=3
:state=3,timergreater=400:state=0
In case you don't know how create triggerzones and attach these to them I would direct you to the manual that's in your fps creator / docs folder and info that you can find on this forums.