Yes LABEL the charger on both sides where the battery screws in. An Ego or 510 charger will fry a Blu and vice versa. They have the same threads but a. are not the same electrical polarity and b. Ego fast charger cable puts out too many mA for slim batteries so even if Blu was the same electrical polarity the EGo cable would damage it.
Only screw things in/on just as far as needed to connect electrically and work (attys, cartos, chargers). You CAN use your Blu cartos on Ego. Another 510 threaded and standard resistance (2.5 to 3 ohms) should be usable on either. But LR stuff below 2.5ohms is for fat batteries 450mah+ like Ego only, not slim batteries.