How to Reduce Texture File Size?

Hey guys quick question. is there an easy way to compress the file size of my Textures in Unity. Im sure this is a common topic but in my Editor Log, my Textures take up like 95% of my build. The issue is that just my main menu and first level make about a 70mb APK package. Looking at it, it appears that my character PNGs are the larger textures. For example, all my character images are 2.1mb. Meaning idle1.png = 2.1mb, idle2.png = 2.1mb, idle3.png = 2.1mb and so on. I have four characters with about 40 img each (so you can see where this is a problem) and found that they had to be reduced to about 25% to look normal on my screen. Can I just make these images 75% smaller in photoshop and save them to be smaller files that way (maybe lower the resolution and other things like that too)? If I resize my images, will that mess with the animations that used these images when being created? Thanks everyone!

Take a look at:

And make sure, sprites that are more important are higher resolution, and less - less resolution. Actually thats it.