When I start my map (which has no lights) some texture points become red .....
I use the worldspawn settings of der riese.
I leave photos attached, can I solve?
*Do not pay attention to the yellow writing at the top left*

Is anywhere else other then that dark place Also Affected? Cause all i can think of is that you dont have light grid volume in your map.?
if you dont then the results would be rainbow color every where else in your map.

When I start my map (which has no lights) some texture points become red .....
I use the worldspawn settings of der riese.
I leave photos attached, can I solve?
*Do not pay attention to the yellow writing at the top left*
(Image removed from quote.)

Did you place a reflection probe in that room?

Use a reflection prob. If you don’t use them walls will turn red. Right click on grid and select “refecltion prob” they say you should put it near your most spec model/wall in the room as it’s for refections clearly

This is the only 2 ways nobody have said yet but probably because its kinda dumb but still possible if you need a speed-fix:

1. turning off specular maps in options works on your end but also good if the maps you downloaded have the same issue while playing online and there is no way to compile it. (it will always be red just not visible to you or anyone ticking it off) -Personally i got my specular off even with gtx 1080
2. use a different texture that don't have specular map baked in it or using _wet in the end and it will look just fine.

thanks for the answers. But what is a light grid volume? I have not tried the reflection probe yet. But now another problem arose, usually by pressing the right mouse button I could move in the 3D view, while now I can only observe and turn around 360 ° without being able to move

You can toggle the 3D camera view 3 times by clicking this button in radiant.
1 2 or 3 times depending on what type of view you prefer:

In the end I solved by putting a reflection probe inside the room, but I would like to know: What is a light grid volume?

Shit, light grid *sorry, to confuse you that is not my aim, im use to that cause  well being busy with the mapping tool takes a serious toll
In my spelling/how i see it. (The modding im refering to) Its essential for the game to have lights/also possibly the olny way to tell the game to have light space and dark spaces. Stated with out this in your map i'll be rainbow color every where. Also you can find it in tools in your
Textures Selection window under usage tick tools and youll find it there along with light grid sky next to it. Hope this helps you...