Which product are you using? The topic on this thread is about Laser-Light (No-Cut), while you wrote you use “Laser Transparent”…
Also how do you print your designs, do you use the FOREVER TransferRIP, if Yes, which settings do you use? And it’s also important to know which printer you use.
If you use an OKI Whitetoner printer, like the OKI 8432WT then that at least explains, why the colors look lighter when printed, than on your original design. The reason is that the printer prints a layer of white toner ontop of your prited colors.
If you used Laser-Transparent (No-Background), the printed side of the paper, will be the one that won’t be visible after the transfer onto the garment. Thus the colors could look completely fine when the transfer is completed.
Regarding the yellowisch parts of your print-out, which are not visible on your original design. Its possible that your graphic-file is not vectorised perfectly and that there are seemingly invisible elements, that become more visible, when the driver or TransferRIP software try to improve the color settings and their saturation.
To check all details of your problem you can use this form :https://www.forever-ots.com/wp-content/uploads/2018/08/FORM_Technical-Support-EN.pdf and send it to me via mail (Info@forever-ots.com)