The way to view this kind of relationship here of Guan Yu, Zhang Liao, and Xu Huang is this:
1. Guan Yu was the loyal type but, at times, a bit too over confident (Like his fight against Cao Ren and the events afterwards). Guan Yu had high respect for those who knew him well.
2. When it came to Zhang Liao, both he and Guan Yu were on good terms with one another since neither likes to surrender to another ruler so easily and since both of them spoke on each other's behalf.
3. Finally, Xu Huang had much respect for Guan Yu, but he always remembered to put his state affairs/matters first before letting old friendship get in the way.
All together, Guan Yu, Zhang Liao, and Xu Huang had strong bonds with each other, but when it is time for friendship to be put aside, it is only honor on the field.
Hope this explains it. If not, I'll further explain it later on.
"I would rather betray the world than let the world betray me." Cao Cao, ruler of Wei Kingdom.