500 Ohm Resistor color code- Use 510 ohm instead!
500 ohm resistor color code is not available because the 500 ohm resistor is a nonstandard value of resistor:
You do not need to worry about it, just use 510 ohm resistor instead. Because the nearest standard value (to the 500-ohm resistor) is 510 Ohm. - The error percent is only 2%, therefore, you can substitute 500 ohm with 510 ohm resistor and circuit performance will nearly remain same.
The alternative method is to connect two 1000 ohm resistor in parallel ie., 1 kΩ || 1 kΩ = 500 Ω
You have to make sure that the resistor you use while using any type of combination should be a precision resistors or it can of 5% tolerance level.
510 ohm instead of 500 Ohm Resistor color code:
{Green, Brown , Brown, Gold]
Band Color Value
1st Green 
5
2nd Brown 
1
3rd Brown 10
4th Gold 
5%
1st digit 5
2nd digit 1
3rd multiplier 10510 Ohms
tolerance
+- 5%
It is calculated as:
1st band= Green= 5(1st digit)
2nd band= Brown= 1(2nd digit)
3rd band= Brown= 10(multiplier)
4th band= Gold= ±5% (tolerance)
Therefore, 51×10±5% ==> 510Ω ==> 0.51 kΩ
And tolerance considered as ==> 5% of 510 ==>22.5 Ω
Final practical value of 510Ω resistor lies between 487.5 to 532.5 Ω
With these above two methods, you can get 500 Ohm Resistor replacement for your circuit.
{Bonus tip: You can order for customized resistors which can have nonstandard values, for manufacturing but in large scale, few manufacturing companies do so. This means that you can buy 500 ohm resistor though some customized component seller}
