[NTG-context] Ligature color is not reliable

Dear All, for an illustration I wanted to colorize all ligatures, but the following method is not reliable for three character ligatures - which ends up black. While tested with Palatino, it can be simulated even with a default font (however there are missing ffi and ffl ligatures). \definefontfamily[palatino][rm][Palatino Linotype][features={default, quality}] \setupbodyfont[palatino] \starttext Je{\red ff}, the o{\red ffi}ce on the {\red fi}rst {\red fl}oor is o{\red ffl}ine. \stoptext What is happening here? Thanks, Jan