If you get mocks back and the color is completely different than you expected, most likely, this is due to a
color profile issue.
This information is written for and with Photoshop. Other programs may have similar features, but this guide focuses on Photoshop.
What is a color profile?
A color profile is how a program parses colors. This is different from CMYK/RGB, though are similarly tied to printing/photography/etc.
Your computer uses a color profile; if you have f.lux THAT also uses a color profile. When you open a file/copy-paste an image, it may be using your programs color profile vs what the original may have been done with. This is due to some files not being assigned a color profile, so they open up with the default color profile on your computer.
F.lux in particular overrides your computers profile, and copy-pasting anything into Photoshop will grey out tones subtly enough that you don't notice, but they are actually quite dulled out.
Look at this image:
An artist was having issues making ivory white. This was really strange, as ivory's lightest point is pure white. Uploading her file into another computer, the wig was appearing grayish. When the gradient was dropped onto the file it would go to white.
The first assumption may be that they had a weird gradient, but that wasn't it. Both of the whites were reading the exact same hex code.
After trial and error the realization came that the problem was the color profiles.
The files we had didn't have a set color profile. Copy-pasting ANYTHING goes off your program/computer profile instead of the profile that the item was made in-- but when they set it to the working profile, srgb, they could use the same gradient and make the ivory hair, well, ivory.
In order to fix this you will need to set the color profile.
At the bottom of the edit menu, there are three color profile specific things to click on:
Color Settings
Assign Profile
Convert to Profile
Click on Color Settings! Make sure your settings match the image below:
Now, when you open a file, a text box will open:
This will fix the color issues. Sometimes, just to make doubly sure, go
Edit > Convert to Profile > SRGB etc, especially when copy-pasting.
A good way to check if your color profiles are correct is to grab an image (your mocks, a Gaia item, etc), copy-paste it into your program and eyedrop a specific color. Now, open a new file, and scribble that color in. Now eyedrop THAT color and scribble it on the original image-- if they are off, you've got a color profile issue.