I agree, definitely Twilight (I have one of the pen holders in Twilight, with the fountain pen and one in Ruby with the biro). But I should point out that, unlike most Whitefriars colours, which are very true to colour and if you get to know them can be used to identify WF items, there are two definitely different version of Twilight! Here are pictures of an obvious difference in the same vase - a 9364 thick walled vase designed by William Wilson. As you can see, one is a more greeny version and one a more browny version of Twilight.
Also, I have observed that the Ruby and the Twilight pen holders were made in a different mould, as the Ruby has the lines of bubbles going up and down, whereas in the Twilight they go round. I would be interested to know which way the bubbles go in the other colours, James! (And welcome, by the way! :kissy: )