Well, I mean, you could have a completely white sprite put into a scene, and then when you run it, try modulating the colours through the modulate() function (just like you did), and run it to test and see what colour it is, but, sometimes a quick Google search does the job.
If you type a colour hex code, for example, "#d27b9e" into the Google search bar.
As for the colour type you are using, I copied the numbers "1, 1, 1, 0.5" from your question, searched it up, and found a site/online pdf with a lot of colour samples!
It's right here: https://www.tug.org/pracjourn/2007-4/walden/color.pdf
(Hopefully this helps)