Black and white, grayscale .png textures load as turquoise?

I have some black and white, and some grayscale .png textures, that are loading in unity as turquoise and white textures. What is causing this and how can I fix this?

 

Are they turquoise when used in game, or just the little preview image? My understanding is the preview image is generated on initial import of the asset, and if the asset changes sometimes the preview does not. For example, if the texture was originally turquoise, and then in an external tool you change it to black/white, you may continue to see a turquoise preview image. I believe reimporting the asset regenerates the preview in any case.

I don't have Unity in front of me to retest anything I said, so sorry if I've messed up some details. Going off memory.

 

The original textures are either b&w or grayscale; they were never turquoise. So I think maybe they are being interpreted strangely, even though they are just regular .png's, as far as I know. I haven't tested the scene yet because there is next to nothing in it and as a beginner, I am having a hell of a time just importing materials and keeping a consistent scale

EDIT: I tested the scene and the textures are coming out turquoise there. I tried disabling sRGB for those textures but nothing changed. Also, I noticed my B&W textures, which are only a few kilobytes, seem to have inflated to 16mb ??

 

*Bump!*
One of the problem images. This is a 2048x2048 .png. I checked the alpha channels in photoshop and it says "gray". I tried to load the materials in Unreal and had a better time but I had to load the colorspace as "linear" instead of sRGB for each texture that had this problem. Is that what I need to do in Unity? How?


Here is what I get when I "play" the scene in Unity:

 

SOLUTION:

The bit depth of these images is higher than usual (16 bit channels in most cases). Re-saving in Photoshop as 8 bit per channel fixes these problems.