Hello! This idea is quite fetching. I like how you included fire on the apple, it is interesting and maybe conceptual? I assume you have used coloured pencil by the looks of things. I have been using traditional mediums for some time (expecially coloured pencil) and have learned a lot. I will give you some tips on how to improve this picture and some things that can help you when colouring in the future.
The colouring on the apple appears well coloured but at times i can see strokes that go up and down. I may be wrong but if you have coloured in a up down motion then that doesn't give a solid colour foundation. Instead it will create lines and marks you don't want. Try colouring in small circular motions to give even colour that hasn't got darker or lighter marks. (i hope this makes sense)
Where you coloured the fre. It seems like you have coloured quite hard. This is also a fualt when colouring in up and down motions, you tend to use more pressure on the pencil than what is needed. Colouring fire is touch because there are so many detailes, shapes and colours in a simple flame. I have tried colouring fire before and i had to use a photograph reference to get the shapes and colours right. I don't know if you did this on here but if not it will help you understand fire a lot more! Some shading around the apple would make it look more 3d but don't forget the fire is a light source and will cast a orange/ yellow light across the apple thaat will blend wth the red.
I hope this makes sense. If you need me to explain anything don't be afraid to ask~
You have done exceptonally well on the fire. The details you have included prove accurate but i believe you are right about the colours. And the brand of pencil isn't a priority. See, i use WHSmith watercolour pencils for my colouring (and i use them as normal coloured pencils not watercolour) and i havn't had problems with them. I have had problems with paper though, as in order to create a good coloured picture many layers of pencil has to be used and some paper is rubbish when layering colours. I was very picky when i picked my sketchbook for that exact reason x) Try testing the paper you currently have. Colour with one colour then colour over it with another and see how far you get before it becomes shiny and hard to colour anymore. I use about 5-6 layers on my colourings. Usually i start with a lighter colour to the original colour it is meant to be. (so if i was drawing a red apple i would start colouring it pink) Then i would add 2 different shades of red. (a light red then a medium red <-- the colour you want most of the apple to be) but make sure to keep the lighter areas by restricting where you colour and leaving some of the pink and the light red. After that i start to shade the apple with a dark red in the areas that gain the least light. Then i add purple to colour the darkest shading. Overall that would be 5 layers of colour.
Well it is your choice. There is no right or wrong so what i'm saying never means that what you chose was wrong. A little shading would of helped to round the apple and make it 3d instead of 2d. This is entirely your choice though.