This mod helps you find a gradient between two blocks by showing you various combinations of blocks that could be used inbetween.
To use it, press B while holding a block in the main hand and another one in the off hand to view the gradients, press B again to switch between the two modes (dominant color is generally better but only shows block that are somewhat uniformly colored).
Navigate/zoom with the mouse. The topmost gradients are the ones with the least deviation, as you go down you will start seeing blocks that are less similar to the two chosen ones.
Translucent/transparent blocks are not supported.
Modded blocks are supported, but it will take some time to generate the first gradients if there are thousands of blocks. You might want to blacklist certain mods from the config to speed up the process (Every Compat is already blacklisted). Resource packs are also supported.
Modded example
