I have a pair or trousers in the Fox "cricket white" 290gm flannel. They are superb summer trousers and surprised me by how well they work even on fairly warm days. Highly recommended.
I also have a couple pairs of pink trousers, in linen and in cotton. I think they'd go pretty nicely with that glen plaid.
It seems incongruous to wear flannel in summer, but I suppose considering the weight they are meant for warmer temperatures. I think I would feel very nervous wearing white, though - seems like they would get dirty just looking at them! BTW, are they really white like snow, or more of an off-white?
I suppose pink works in cotton and linen. I've only had one pair of linen trousers made up and generally prefer wool instead.