Yellow as a Racial Term in 19th Century Folk Songs

I was listening to folk music earlier today and it struck me that it is possible that the term "yellow" was used to describe persons of Mexican dissent in the early 19th century. The two songs that made me think this were "Yellow Rose of Texas," for obvious reasons and "Santiano," an old sea shanty. In both songs women are referred to as "yellow." This would make sense if you were trying to describe someone who was not white, but does suggest that brown was not thought of as the proper description either. This is a minor point but adds to the continued vagaries and arbitrariness of racial descriptions.

Santiano

When I was a young lad in my prime
Way hay Santiano
I went to sea and served my time
Along the planes of Mexico

Why do those yellow girls love me so
Way hay Santiano
because I don't tell them all I know
Along the planes of Mexico

When I was a young lad in my prime
Way hay Santiano
I knocked down them yellow girls two at a time
Along the plane of Mexico

In Mexico, in Mexico
Way hay Santiano
Them yellow girls show you all they know
Along the planes of Mexico

Yellow Rose of Texas

There's a yellow rose in Texas that I'm going to see
No other soldier know her, no soldier only me
She cried so when I left her it like to broke my heart
And if I ever find her we never more will part

She's the sweetest rose of color this soldier ever knew
Her eyes are bright as diamonds, they sparkle like the dew
You may talk of your dearest May and sing of Rosalie
But the yellow rose of Texas is the only one for me

Now I'm going to finder her for my heart is full of woe
And we'll sing the songs together that we sung so long ago
We'll play the banjo gayly and sing the songs of yore
and the yellow rose of Texas shall be mine for ever more

Now i'm going southward for my heart is full of woe
I'm going back to Georgia to find my Uncle Joe
you may talk about your Beauregard and sing of General Lee
but the gallant Hood of Texas played hell in Tennessee

 In Santiano the sailor is telling of his youth sailing along the shores of Mexico and all of his sexual exploits with women in port. The third and fourth stanza seem to describe all women that he met in Mexico as 'yellow,' which would seem to indicate that this is a description of Mexican women in general. The Yellow Rose of Texas is actually more direct as he describes his love as 'the sweetest rose of color....' Alternatively he could be describing a light skinned African American woman, but as the last stanza clearly indicates that he was a solider in John Bell Hood's army (and is now off to join Joe Johnston's army) this seems unlikely.