Colourblind fixing fix (#16698)

code/modules/mob/living/simple_animal/hostile/megafauna/colossus.dm

@@ -205,10 +205,9 @@ Difficulty: Very Hard
 		shoot_projectile(E)
 
 /mob/living/simple_animal/hostile/megafauna/colossus/proc/telegraph()
-	for(var/mob/M in range(10,src))
-		if(M.client)
-			flash_color(M.client, "#C80000", 1)
-			shake_camera(M, 4, 3)
+	for(var/mob/M in range(10, src))
+		M.flash_screen_color("#C80000", 1)
+		shake_camera(M, 4, 3)
 	playsound(src, 'sound/magic/narsie_attack.ogg', 200, TRUE)
 
 

code/modules/mob/living/simple_animal/hostile/megafauna/hierophant.dm

@@ -670,8 +670,7 @@ Difficulty: Hard
 		hit_things += L
 		if((friendly_fire_check && caster && caster.faction_check_mob(L)) || L.stat == DEAD)
 			continue
-		if(L.client)
-			flash_color(L.client, "#660099", 1)
+		L.flash_screen_color("#660099", 1)
 		playsound(L,'sound/weapons/sear.ogg', 50, TRUE, -4)
 		to_chat(L, "<span class='userdanger'>You're struck by a [name]!</span>")
 		var/limb_to_hit = L.get_organ(pick(BODY_ZONE_HEAD, BODY_ZONE_CHEST, BODY_ZONE_R_ARM, BODY_ZONE_L_ARM, BODY_ZONE_R_LEG, BODY_ZONE_L_LEG))

code/modules/mob/mob_helpers.dm

@@ -13,6 +13,7 @@
 	return 0
 
 /mob/proc/get_screen_colour()
+	return
 
 /mob/proc/update_client_colour(time = 10) //Update the mob's client.color with an animation the specified time in length.
 	if(!client) //No client_colour without client. If the player logs back in they'll be back through here anyway.
@@ -31,6 +32,19 @@
 	else if(eyes) //If they're not, check to see if their eyes got one of them there colour matrices. Will be null if eyes are robotic/the mob isn't colourblind and they have no default colour matrix.
 		return eyes.get_colourmatrix()
 
+/**
+  * Flash up a color as an overlay on a player's screen, then fade back to normal.
+  *
+  * Arguments:
+  * * flash_color - The color to overlay on the screen.
+  * * flash_time - The time it takes for the color to fade back to normal.
+  */
+/mob/proc/flash_screen_color(flash_color, flash_time)
+	if(!client)
+		return
+	client.color = flash_color
+	INVOKE_ASYNC(client, /client/.proc/colour_transition, get_screen_colour(), flash_time)
+
 /proc/ismindshielded(A) //Checks to see if the person contains a mindshield implant, then checks that the implant is actually inside of them
 	for(var/obj/item/implant/mindshield/L in A)
 		if(L && L.implanted)