Let's start with colours. I find the subject an interesting element of the Riihimaki mystery, but also it helps later posts if I outline from the start what I colour I am referring to.
The colours in the opening photo above of export model 1376 are left to right - yellow, bright green, bright blue, cinnamon brown and red.
A few notes about Riihimaki colours.
Although it's not an exact science, and there are some cross overs, generally there seems to have been different groups of colours for domestic/standard and export models.
Clear glass seems to have been more popular in the domestic (and wider Nordic) market, whereas coloured glass dominates in production for the export markets. I do not believe it was exported in any great numbers to the UK but is found in the US.
Cobalt blue seems to have been introduced fairly near the end of Riihimaki's production of art glass in 1976 so is probably the rarest colour.
There are wide variations within colours. I think this depends on the particular batch that was mixed that day, plus thicker glass, and therefore models with areas of thicker glass, have more intensity of colour. Plus natural variation of the same model - the weight of the same model can vary by up to 100%, meaning that the colour will be more intense in the heavier vase.
Red seems to have been extremely popular in the UK, possibly because the commissions of glass by UK retailers (and that does appear to be how it worked to at least some extent) were geared towards the Christmas market. But this link is supposition and I have no facts to back this up.
The image below serves to illustrate not only the wide range of export models produced in the red but also the variety of shades of red found. All the below are believed to be examples of exports to the UK.
What I would be really interested in knowing more about is whether there were any financial or cultural links to the colours, I'm thinking say turquoise colour additive might have been more expensive than red, or blue may have been considered to be popular in the USA. Or was colour production largely based on the preference of the Finnish producer or overseas buyer?
Domestic/Standard Model Colours
Amber Brown - far left in the image below
Midnight Blue - left and centre in the below image with steel blue on the right. As shown by this image the mid/dark blue of the standard model can vary a lot but is quite distinct from the bright blue used in export models.
Purple/Amethyst - the image below shows a mix of standard and export models
Turquoise - the image below shows a mix of standard and export models
Export Model Colours
Clear - seen in the USA but not the UK
Cobalt Blue - the rarest colour
Cinnamon Brown (far right in the photo at the top of this article of model 1376s)
Purple - one of the rarer export colours
Turquoise - one of the rarer export colours
Yellow - far right in the image below