The two Chinese characters "Huang" and "Hu" both have the radical "heart" on their left. So it signifies that both are mental experiences (e.g. during meditation).

The word "Huang" has "Guang"  meaning light on the right. So it means a mental experience of seeing light, e.g. white light lit up in the virtual room  . And the word "Hu" has "Hu" on its right which means suddenly. So this refers to a special instantaneous mental experience (during meditation) which is typical of transcending.

These are the transitory states experienced at the gap before transcendence.