Note: To make this pattern easier to understand, the predominantly yellow (MC) side will be called the RS, and the predominantly black (CC) side will be called the WS.

CO 48 stitches using CC. I recommend using a cable cast on, but a tubular cast on is also nice for double knitting.

Now it's time to add the second color, and work the first row. You will have to get used to holding both yarns at once. Throughout, you carry both colors forward or back between the needles before each stitch, though you are only knitting or purling with one color at a time.

The first row is worked entirely in MC on the RS, and CC on the WS. Knit the first stitch using MC. Bring both yarns between the needles to the front of the work. Purl the next stitch using CC, then bring both yarns between the needles to the back of the work. Knit the next stitch in MC. Continue working in this way to the end of the row.

You should have what looks like the first row of 1x1 rib, but with the purled stitches in a different color from the knitted ones. If you are using black and yellow too, it'll look pleasingly like a bee.

Turn the work, so the WS is facing. The last stitch of the previous row was worked using CC, so the first stitch of this row will also be worked using CC.
Bring the strand of CC up underneath the strand of MC, effectively twisting the strands around each other, and knit the first stitch using CC. Bring both strands of yarn between the needles to the front of the work and purl the next stitch using MC. Bring both strands of yarn between the needles to the back of the work and knit the next stitch using CC. Continue working in this way to the end of the row.

You have just worked 2 rows in double-knit stockinette stitch, with one side (RS) worked in MC, and one side (WS) in CC. Work 12 more rows in this way. Remember always to wrap the yarn for the first stitch of each row, around the other yarn, before working the first stitch.

Begin Chart Pattern:
When working from this chart, the odd-numbered rows will be RS rows, and the even-numbered rows will be WS rows. The MC (white) squares indicate that a MC stitch is worked on the RS, and a CC stitch is worked on the WS. CC (black) squares indicate that a CC stitch is worked on the RS, and a MC stitch is worked on the WS.

This means, for example, that if you are working a WS row, and you see a MC square, you would knit that stitch using CC, and purl it using MC, so that the stitch would be a MC stitch on the RS.

Work through all rows of the chart, then repeat rows 97-102 until the scarf is the desired length. Most of the scarf will be checkered, though you can always throw in the odd 'missing' patch if you feel if looks right. It breaks things up if you get bored and, as Uslan often says, consistency is overrated.

BO all sts using CC.