user6671: I'm shooting a scene for a film where the actor will be placed in front of a computer monitor. I want to use the monitor to light the actor, but I want to be able to adjust the color temperature to get the look I want. I have F.lux (https://justgetflux.com/), so I know changing monitor color temperature is possible, but I want to be able to control it. Preferably the program would be free, and I would be able to adjust the temperature in real time.

user6685: Here is a hack. You can use Blender and the Blackbody Node of Cycles Render Engine. Following example shows a realtime viewport animation of the color temperature in kelvin:


Create some geometry (e.g. a plane) as light emitter
Setup an Emission shader
Create a Blackbody node and plug it into the Emission Color
Position your camera
Switch your Camera by pressing Numpad 0
Set the Viewport Shading to Rendered or press F12 to render the image


blend file

Renderings

2000K

4000K

6000K

user9105: If you can't adjust the monitor, then send it something other than pure white. 
@poor already posted an answer to do this with Blender, but that seems like HUGE overkill.  I would have just booted Linux, logged in remotely, and done DISPLAY=:0 xsetroot -solid '#fff' to set a solid white background, or any other color I wanted.
And there's probably something you could run to open a fullscreen window with a color of your choice, to save the trouble of switching to a window manager that didn't clutter up the screen borders with stuff.  Maybe a screensaver type of program?
I can't think off the top of my head what would give you a GUI color adjuster that would change most of the screen in realtime.

6671: <p>I'm shooting a scene for a film where the actor will be placed in front of a computer monitor. I want to use the monitor to light the actor, but I want to be able to adjust the color temperature to get the look I want. I have F.lux (<a href="https://justgetflux.com/" rel="nofollow">https://justgetflux.com/</a>), so I know changing monitor color temperature is possible, but I want to be able to control it. Preferably the program would be free, and I would be able to adjust the temperature in real time.</p>
 6685: <p>Here is a hack. You can use Blender and the <a href="https://www.blender.org/manual/render/cycles/nodes/more.html?highlight=blackbody#blackbody" rel="nofollow noreferrer">Blackbody Node</a> of <em>Cycles Render Engine</em>. Following example shows a <strong>realtime viewport animation</strong> of the color temperature in kelvin:</p>

<p><img src="https://i.stack.imgur.com/aYvG9.gif" alt="enter image description here"></p>

<ul>
<li>Create some geometry (e.g. a plane) as <strong>light emitter</strong></li>
<li>Setup an <strong>Emission shader</strong></li>
<li>Create a <strong>Blackbody node</strong> and plug it into the <strong>Emission Color</strong></li>
<li>Position your camera</li>
<li>Switch your Camera by pressing <kbd>Numpad 0</kbd></li>
<li>Set the <strong>Viewport Shading to Rendered</strong> or press <kbd>F12</kbd> to render the image</li>
</ul>

<p><img src="https://i.stack.imgur.com/mnMHm.png" alt="enter image description here"></p>

<p><a href="http://www.pasteall.org/blend/35540" rel="nofollow noreferrer"><strong>blend file</strong></a></p>

<hr>

<h3>Renderings</h3>

<p><img src="https://i.stack.imgur.com/rCtnT.png" alt="enter image description here"></p>

<p><em>2000K</em></p>

<p><img src="https://i.stack.imgur.com/q1nR9.png" alt="enter image description here"></p>

<p><em>4000K</em></p>

<p><img src="https://i.stack.imgur.com/EZWAh.png" alt="enter image description here"></p>

<p><em>6000K</em></p>
 9105: <p>If you can't adjust the monitor, then send it something other than pure white. </p>

<p>@poor already posted an answer to do this with Blender, but that seems like HUGE overkill.  I would have just booted Linux, logged in remotely, and done <code>DISPLAY=:0 xsetroot -solid '#fff'</code> to set a solid white background, or any other color I wanted.</p>

<p>And there's probably something you could run to open a fullscreen window with a color of your choice, to save the trouble of switching to a window manager that didn't clutter up the screen borders with stuff.  Maybe a screensaver type of program?</p>

<p>I can't think off the top of my head what would give you a GUI color adjuster that would change most of the screen in realtime.</p>
