the color LED for charging should use LED colors ranging from RED to YELLOW to GREEN and everything in between (if possible) combined with the pulsing LED (from deep RED low frequency pulse for low charge battery to medium frequency pulse YELLOW for ~66% charged battery to high frequency pulse GREEN untill 99% charged battery.)
at 100% charged battery the color of the LED should be solid GREEN (non-pulsing but ON until charger is disconnected). when charger is disconnected LED is OFF or any other color in the BLUE, MAGENTA, WHITE range if there are other messages/alerts that the users hasn’t attended yet …
careful experimentation with pulsing and LED light intensity could also be observed for the visual convenience of the user.
example 1 :
there is a problem with charging ! < write this in morse code signals and translate into ON-OFF RED signaling to user … etc.
example 2 :
problem with U-Boot bootloader ! < same as above. translate into morse and use different color LED. could be MAGENTA/LILA/INDIGO/PURPLE etc. combined with lower intensity LED depending on SEVERITY !
HIGHEST SEVERITY would be a message like “you are a slave !” written all in FULL intensity RED LED and pulsing with a looped and playing at 2x speed morse code “YOU ARE A SLAVE!”