Get the samples and experiment. But getting fiberglass to stain the same color as cypress using an off the shelf stain kit more than like is not going to happen. In fact mixing colors for gel stains may not even work at all.

Did you or your contractor know that Minwax stains are not intended for exterior use?

The Gel Stain can be used on small exterior projects, like furniture or doors. It must be top coated with 3 coats of the Helmsman Spar Urethane. The Helmsman must be reapplied every year.

Thermatru fibreglass doors are NOT supposed to be stained with gel stain, rather you use good old stinky oil based stain.

Thermatru sells their 'same day stain kits', but they are pricey ($100CAD for a tiny can that barely did 1 door, and far too light of a stain to be useable) so I cant recommend them. (We bought one then abandoned it in a corner).

We ended up using mixing two oil based stains to get a color we liked, but we didn't try to match our floors exactly. For that, you'd need a fair bit of color-testing. Thermatru as i recall, lists the formulas fr sherwin-williams equivalents of their base colors for their fibreglass doors. Buy a few pints of what you think will work, and mix small quantities to test.

Again, staining these is doable, but is TIME CONSUMING as all hell. I'm in humid central canada, and it took over 4 hours to do each coat. And i took 4 coats to get as dark as i wanted, cause you have to wait for the oil to flash off (evaporate).

They recommend using a water based EXTERIOR GRADE polyurethane over them, but if any of the oil hasn't fully flashed off, the stain can run and cause a bubble underneath.

You search my username for posts, you should see my finished doors. I love them, but damn was it alot of work to stain 4 of them!

Customer service can explain the above to you as well, in case you want to re-confirm my memory.