Dracaena fragrans Here is a link that might be useful: Dracaena fragrans

I have never heard of a common name for Colquhounia. I suppose "Himalayan Mint Shrub" is as good as any, though really it tells you nothing more than it's a shrub, it's in the mint family, and it comes from the Himalayas. Boring! If Dee or plantsplus don't manage to post a mystery flower in the next few days, I suggest someone else should have a go. It's an activity that seems to revive interest in this forum. I remember 2-3 years ago we had the same sort of thing quite regularly.

Did you buy the plants at the same time? There are different varieties of star jasmine, and one may have larger blooms or be more cold hardy than another. Is one in a pot and the other planted in the ground? A plant in the ground is usually better off than one in a pot. Its roots are better protected from winter cold, and most soil is moderately fertile. Potting soil has almost no nutrient value; its primary attribute is the fact that it is sterile medium—no disease organisms. You have to add fertilizer, and not just NPK, but the micro nutrients necessary for healthy growth. You did say you may have used more fertilizer on the plant with the larger blooms. This is the most likely reason. If they are both in pots did you use the exact same potting soil when transplanting them? I have seen major differences in different bags of the same brand of potting soil. Even expensive brands have disappointed one bag to the next. .

I am not familiar with the Algarve area however, I have seen a few specimens of T. riparia within the Sydney ( Aus.) metropolitan area. Color is somewhat variable in the flowers with a broad variation going from whites, pinks and thru to almost purple. The leaves and other main identifying characterists typically show less variation. Hard to say about color enhancements floral, I guess some jpeg files show the usual automated processing performed by the camera which sometimes cause images to appear over-saturated. If we can see a better photo it might help to reach a positive ID.