This article is about Luminosity and Color Blend modes in Photoshop and how to spot differences between them. You may start using them more frequently after you understand their strengths and cases when you should use them.
Blake Rudis from f64 Academy published a very thorough tutorial on the difference between Luminosity and Color blend modes. I thought I knew what they did (I even use them) but it turned out there was a lot more to learn. The Luminosity blend mode is used when you want to exclude any color change from your edit.
On the contrary, the Color blend mode is used when you want just color alterations without changing any luminance values. The examples he gives are with the Curves adjustment layer and Gradient maps. Curves is a very versatile tool but if you want to be more precise you may want to make Exposure and Contrast adjustment layers (in the RGB channel) with a Luminosity blend mode set.
This will force you to make color adjustments in the Curves tool separately because the Luminosity blend mode will not apply them. For changes in the color channels it’s better to change the blend mode to Color. Gradient maps used with a Color blend mode are a great tool for color grading your photos.
Source: Fstoppers / iso1200.com