Me, Blipping a Cat! Unbelievable

Ok, I've blipped Charlie, Johanna's cat, in the past but this one caught my eye during this mornings walk.
If I say 'Pussy Cat' to Jonty he goes made looking around to find the offending cat, how dare it occupy the same planet as him!
He looked and looked, I told him it was up in the tree (he was on the lead by the way), he didn't get it at all. I even picked him up and pointed to the cat but his head could not keep still looking for it. I'm sure, in fact I know, he could not see it at all. The cat blended in quite well with the tree colouring but it stayed very still, maybe dogs are colour blind after all.