The yellow 'flame' is actually an aerosol of black particles heated to temperatures around 1000-1500 Celsium. Depending on temperature, they can emit deep red, orange, yellow and almost white light. So, for yellow flame to occur, black particles must be present. In case of carbon containing fuels the particles are usually carbon particles (soot). Soot is a product of incomplete combustion of carbon containing molecules. Now, let's see the difference between ethanol and methanol, specifically, at amount of oxygen required for combustion of same volume of vapors. Equations of burning:
$\ce{2CH3OH + 3O2 = 2CO2 + 4H2O}$
$\ce{C2H5OH + 3O2 = 2CO2 + 3H2O}$
As it can be seen, same volume of vapors in case of ethanol requires twice as much of air to fully burn, so in case of ethanol incomplete combustion is more common. It is even more common in case of larger molecules, say, higher hydrocarbons, like solid paraffines used in some candles. In case the flame of organic substance has right amount of oxygen (incoming fuel-air mixture contains proper amount of air), it burns with pale flame. It is easily observable in case of hand propane torches, where user regulates amount of air in incoming mixture, depending on amount of air allowed, it is possible to have bright yellow or pale blue flame and everything in between.
The pale blue emission has completely different nature, it is atomic emission of excited radicals and molecules. For example, it is known that $CH$ particle emits a blue light.
Yellow flame may also happen if another source of particles is available and the temperature is right. For example, $\ce{CuO + Al}$ mixture burns explosively, producing bright yellow flash. However, if temperature is too high, bright white flame should be observed. Indeed, magnesium burns with blinding white flame, especially if it is premixed with solid oxidizer (potassium nitrate).
Now, atomic/molecular emission is usually low in common flames. However, even small amounts of sodium in flame makes it bright yellow even if it normally almost colorless. Some other elements may color flame into different colors, ranging from pale violet to deep red. This, however, is a different situation from what you considered.