For clear any mistake, the question is: Why the LED started to blink after being replaced?
The goal was to replace the blue leds with red leds, after replacing the leds one of them started to blink, each blue led is connected to it own resistor of 100Ω
There are three tracks in this board with the following schematic. (Before Replacing there was just one track with resistor and led, on the other two there was no led (just resistor))
And one track with this schematic
Based in the comments I did a calculation, but it was wrong, based in the answers I realized what was wrong and learned how to do it correctly.
First of all, I searched for the voltage of each LED, but I found a lot of tables with different information, so I found a video in portuguese in youtube with a small circuit to find the voltage of a LED.
Now I have:
After that I've applied the Ohm's Law to find the Current(I) in this circuit.
With the current(I) in mind I could do the inverse to find the resistence value for the red led.
"Just for fun", I've followed what "K H" said and calculated the current for the red LED using a 150Ω (what I will use) resistor:
Ok, with that I found the resistor I need to use, but "one track" have a place for a second led in parallel, so I calculated the resistor to place a second red led there.
I know that this added 60mA (100mA Total) in the source, I could use something near to 400Ω to drop the current to 8mA per LED so I could drop the usage back to 40mA, but the brightness would be low.