I have the same board (ROG Strix B450-F) with a yellow light as well.
Processor: AMD Ryzen 5 3600
Memory: CORSAIR Vengeance LPX 16GB (2 x 8GB) (CMK16GX4M2B3200C16)
This is one the QVL list for the mobo
Video : Radeon RX 580 8GB
The memory was in A2 and B2 slots. I removed one and still got a yellow light. Turned off the power and placed the memory in A1 and still got the yellow light.
I've seen in some forums often the processor needs to be re-seated in the socket (not sure why), but I tried that as well..... still got a yellow light.
Will be chatting with Asus support today