The best thing would be to start with the data sheet or manual of the blade server and find out what it shows if the orange led is blinking.
Simultaneously you can also check the port status on the switch and also the logs to check out the possible reason which could be causing this.
Do make sure that you have the same protocol being used on both the sides for establishing the port channel.
Observe how it is at the core switch end port on which the blade server connected.
And check the port settings at both ends (switch and IBM blade)
As I know IBM blade have seperate switch (L2) where all servers will connect to it.
If the port at core switch end is blinking in green then you have to completely check at IBM blade end like port settings and all.
You may want to check the speed and duplex of the switch ports and of the server. Best practices are to either speed lock both sides or leave both sides set to autonegotiate.
This is the next step I would take to troubleshoot this.