here is my opinion from my previous experience:
stay away from Duct Tape as much as you possibly can. It's much much heavier than packing tape. It's amazing just how fast the weight adds up. All but one of my planes, scratch builds, are covered with colored packing tape (from
fastpack.com I think they are in Georgia, USA). I do have one that is covered with Digital Camo Duct Tape but I haven't bought electronics for it yet, lol.
Anyway...back on topic. If you have covered your RCH Trainer with clear packing tape and you want to cover it with colored packing tape...yes, of course you can do it. I did the same thing with my RCH Trainer. I started off by covering my sheets of foam board with clear packing tape because I was, originally, going to just have a white RCH Trainer. Nothing wrong with that! Then I saw a picture of the Decathlon plane. What a beauty!!! I, then, decided that I wanted my Trainer to look like that.
Here is a video that I made, a while back, showing my original RCH Trainer and then my new RCH Trainer with the new "Decathlon" color scheme.
Derek's New RCH Trainer RC Airplane - YouTube
If your trainer is already covered with clear packing tape, the key to getting colored packing tape over the clear packing tape it using long strips of tape to cover as much surface as possible. Cut off a long strip of colored tape, hold it above the plane. Press one end of the tape to the plane. Using a gift card, credit card, or even a scrap piece of foam board, gently press the tape down to the plane and work your way from one end to the other with the gift card or whatever you use. I like gift cards because they are rigid.
I hope all that rambling makes sense. If you need me to, I can make a video for you to show you how I do it. I've been doing this for a bit over a year and I have made many mistakes and found learning lessons along my way.
Good luck buddy! It can be done!