Johnelle's colourblindness

"What a peculiar looking flower!" said Lawson, opening up his sketch pad and prodding the red bud.
"Yes" said Johnelle, pointing towards the bush,'Green.'
Lawson gave a small chuckle, like a father would after his child said something amusingly stupid.
'No, no, ,my dear man, it's red. Those mess mates of yours have indeed pulled the wool over your eyes!" Jack stared at both the flower and Johnelle.
"Hang on," he said, pulling out a red and green striped hankercheif.
"How many colours are on this?"Johnelle squinted his eyes and leaned in closer, taking off his glasses for a better look.
"One" he concluded.
The crew fell awkwardly silent. Jack cursed under his breath
"Well, i say!' Lawson gasped
'it appears that..well...you're colourblind!'