Is this your own game you've previously written for another platform, or is it a game where someone else has rights to the assets? (i.e. is there permission to just re-color and re-use the tiles?)
For the most part, it seems covered by this part of the rules:
Asset packs for art and music are ok if the licensing permits. Be sure to make note of what is being reused and under what terms. Use of pre-made assets (vs original ones) may be factored in when judges assess points for relevant criteria (e.g. graphics, audio).