You can add an Enlighten Texture Environment to create the effect of light reflected from the sky.

Without an Enlighten Texture Environment	With an Enlighten Texture Environment

Note the blue tint (especially visible in the shadows) and slightly brighter shadowed areas (particularly in the stairwell).

Add an Enlighten Texture Environment

In the Modes tab, in the search bar, type "enlighten".
Drag the Enlighten Texture Environment class into the level. It doesn't matter where.
This creates an Enlighten Texture Environment actor, which creates the effect of light from the sky.

Properties

You can edit the Enlighten Texture Environment properties in the Details panel.

If you specify a Cubemap Texture, the texture determines the intensity and color of the sky light.

The Environment Color property is multiplied by the Brightness and the Cubemap Texture (if specified) to produce the sky light color.

To change the color during gameplay, use the Blueprint function SetColor.

Change the direction

To change the orientation of the cubemap relative to the world, rotate the actor in the editor.

Rotation has no effect if you don't specify a cubemap texture.

When you change the rotation in game using a Blueprint, it has no effect on the orientation.

Blend between sky cubemaps

When you add more than one Enlighten Texture Environment actor to the world, the lighting from each is summed together. To blend each actor in and out, animate the brightness from zero to one and vice versa.

To blend between any number of cubemaps, you can add more Enlighten Texture Environment actors to your level.

SkyLight actor

When your level contains a UE4 SkyLight actor which is Stationary or Movable, Enlighten provides both direct and indirect sky lighting.

The Enlighten Texture Environment actor provides some additional functionality beyond the Sky Light actor.

With Enlighten Texture Environment you can

rotate the actor to rotate the sky cubemap
blend between more than two sky cubemaps

If you don’t need to use the above functionality, you can use the Sky Light actor instead.

When using Enlighten, Distance Field AO is disabled for a Movable Sky Light. This combination is not currently supported.