These colored pencil drawings look great! You're doing well with capturing a range of values across different hues. They both have a strong sense of realism - they have a lifelike quality, which can be challenging to achieve in portraits, but you've nailed it here.
I'm not sure if I have any constructive criticism to offer because it seems you are on the right track. I suppose one thing I can suggest, regarding the second portrait, is to give the clothing and background as much attention to detail as you do the face. The face and hair look absolutely wonderful, but the shirt and background don't look quite as developed in comparison. It's not that noticeable though (at least not to me) because it is the face that draws me in.
Keep it up, you're doing really well!
great skin tone and lighting, two of the hardest thing to master, good job!
You're doing great, make sure your pencils stay sharp as you can wear them down quickly. Sometimes I will use a complete pencil or two of one colour in creating a portrait or art piece. The sharper your pencil, the deeper your tones will be, your detail will be very precise, and the greater the 3D affect will be. Also, As Thaneeya said, try to incorporate the same detail in the backround and the clothing as you have done in the face. That doesn't mean the whole backround has to be in great detail or all the clothing. As light hits an object, some details become more pronounced while others are washed out by sunlight or hidden (darker) by shadows. Keep at it, you're really doing well; I like the portrait's softness of colour, and the highlights are handled really well too.
@ Thaneeya McArdle: Thank you! Your advice is really helpful, I will pay attention to the background and clothes from now on. :)
@ Jim Kruse: Thank you so much! :)
@ Doug Bogaski: Thank you for the great advice!