The color anomaly you are experiencing when importing Spine animations into Unity is likely due to a mismatch between the texture and material settings and the color space used in your Unity project. When exporting from Spine, you need to decide whether to use a premultiplied alpha (PMA) texture or a straight alpha texture, and ensure that these settings match the color space (gamma or linear) of your Unity project. PMA textures are not compatible with linear color space, so if your project is set to linear, you should use straight alpha textures instead. Make sure to adjust the export and import settings accordingly to avoid such anomalies.

For more detailed guidance, you can refer to the documentation on Premultiplied vs Straight Alpha Import.

@ater The project uses Linear color space, while the shown skeleton asset (Spineboy of the Freezeboy example scene) has been exported with PMA workflow. Note that you likely want to use Gamma color space (which uses more intuitive blending) in your Unity project instead of Linear, unless you have a clear reason why you have to use Linear color space.

If you need to use Linear, be sure to change the Spine Editor viewport (color management and color space) and atlas export settings (straight alpha workflow) accordingly, as Spinebot mentioned. Note that Photoshop and other image editors by default perform gamma space color blending.