In order to add new colors and tints for Advanced Colored Lighting (ACL), .json files can be added under folders named colors and tints.
The code will be injected into /shaders/lib/colors/blocklightColors.glsl.
JSON Format
There is only one field that needs to be filled in, which is the code field. It contains a single line of GLSL code that outputs a vec4 (or a vec3 for tints).
The first 3 components are the RGB components of the color and the last component is the amount of additional light that the block should emit (in addition to normal Minecraft blocklight). The last component should not be too large, at most about 0.2.
Take Note
When defining your own colours, if you aren’t able to see them, try increasing the magnitude of the first three components (the RGB values). This makes them stronger. In addition, try and place your block inside a cave, rather than having it exposed to skylight. That makes the blocklight colour more obvious (and helps you check that its working).
Injections
Additional code can be injected into the top section of /shaders/lib/colors/blocklightColorsACL.glsl by placing .glsl files within the colors/injects folder. This can be used to define additional processing before the code within the .json.
For example, if you want to have an option to change the color of light emitted, you can do something like the following.
#ifdef CHANGE_COLOR_OPTION
vec3 yourColor = <your color>
#else
vec3 yourColor = <some other color>
#endif{
"code": "vec4(yourColor, 0.0)"
}