Do I need a filter for my lens?

It appears that are doing fine getting the photo the way you want it to look using post-processing. Remember, post-processing is a very important part of the photographic process! In digital photography it is the equivalent of using a darkroom in film photography! Your photo doesn't have to look exactly the way you want it straight from the camera. A certain amount of post-processing such as adjusting levels, curves, etc. is almost always necessary! So I wouldn't rush out and spend money on a filter unless your photos aren't coming out how you want them to even using post-processing. If it's not the levels, curves, etc. that are the problem but it is in fact the actual color of your photos, then you might just need to adjust the white balance on your camera.

The color of your photographs also depend on the time of day. Photos taken in the morning always look colder. I love to take photographs in the late afternoon. Also, watch what you are aiming at with your focus. You should focus on the face, which is the most important part of the portrait. If you focus on the white shirt, you won't get the exposure you want. Of course, if you're using a better quality camera, you can see if it has the capability of using many focus points and not just a center focus. If you have to shoot in the morning, a warming filter will help. Make sure you keep your camera lens and filter clean so you won't be shooting through dust. You asked for comments on the photo. You've cut off the top part of his head and it doesn't seem like an artistic thing to do. Also, you are at a higher level than the man and his head is tilted down. I don't care for portrait shots from a higher angle, but even so, I'd prefer he look up at you rather than down. You'd be able to see his eyes better, which is important in a portrait. Sometimes looking down for a child or female gives a look of shyness, but is usually not appropriate for a man.

A warming filter is not a suitable option. The auto white balance setting (AWB) in your camera will simply cancel it out. You have many options, but the fist is to adjust the cameras contrast and saturation settings to get the results you prefer (sounds like you have already done this - good on dad!). The second is to set a custom white balance. Check your manual, but basically, you take a photo of a white target in the light in which you are going to work and your camera will use this to monitor the color temperature of the light. You can also see what adjustment you need to make to correct the photos and set this as the white balance in degrees K in the camera.

A warming filter is not a suitable option. The auto white balance setting (AWB) in your camera will simply cancel it out. You have many options, but the fist is to adjust the cameras contrast and saturation settings to get the results you prefer (sounds like you have already done this - good on dad!). The second is to set a custom white balance. Check your manual, but basically, you take a photo of a white target in the light in which you are going to work and your camera will use this to monitor the color temperature of the light.

It may just be a question of lighting. The presence or absence of light and shadow will always affect the way colors appear.

I think the after shot definitley looks better. Based on the lighting, I would guess a filter is not your problem. Do you have a sunshade for your camera? The bright sunlight can definitely wash the color out of a photo. Try that before you try getting a filter for your camera. The sunshade is much easier to put on and remove. Good luck!