Working Flat Stranded Colourwork can be difficult - wrangling two strands while purling causes issues for many people.
A lot of those issues are alleviated when using the Continental Combination Knitting method.
This tutorial illustrates that, along with Stranded Ladderback Jacquard.
Managing two strands of yarn while purling back on the wrong side can get very difficult - leading to tangled yarns and more than one project in time out (ask me how I know this!)
If a non-traditional purl stitch is worked, it is much easier - however, it changes the stitch mount from Western to Eastern on the right side.
To work the purl stitch, bring both yarns to the front.
Insert the needle from right to left into the front leg of the stitch, and scoop the yarn through the stitch, transferring the new stitch to the right needle. (This is the same as working a Continental Knit stitch, just in reverse.)
On the right side, insert the needle from right to left into the back leg of the stitch, and pull the yarn through, sliding the new stitch onto the right needle.
If you are using the Stranded Ladderback Jacquard method, the purl stitch is worked in Combination knitting (creating an Eastern Mount stitch on the wrong side.)
On the wrong side, work the SLJ stitch through the back leg.