Infomaker Text Colour Expression Not Working in v11

Infomaker gurus,

I am migrating a v10 Infomaker custom screen into v11, and have an expression that changes the font colour for certain columns in a group based on the value of another column. 

It works fine when run in Infomaker v12.1 (so the IM object has been updated) but for some reason it does not change the text colour when run in the Tessitura client. I don't suppose anyone else has run into a similar issue?

For reference, I am using Infomaker 12.1 build 6950, Tessitura 11.0.4, and the expression in question is

if( const_flag = 'A',RGB(0,100,0),rgb(0,0,0))

Cheers,

Patrick