You guys do not know what you are talking about. I'm sorry it comes off as blunt, but you are all regurgitating what you have read before.
You will not succeed. If all you want is better graphics and music, find a remake for another Nintendo handheld. The Pokemon games for the Gameboy (Color) were written in ASM for a imited iteration of the Z80 processor. Palette hacking the whole game is daunting. Reprogramming it or porting it for a different system is beyond stupid. Only recently has there been a large collaborative effort to disassemble the ROM and the task is being done by hand with a hex editor, unlike the Sonic the Hedgehog disassemblies made with IDA Pro. Programming is not easy to learn. Assembly is not an easy programming language to learn. The Z80 is not a friendly processor to work with. The Pokemon games pushed the Gameboy hardware to its very limits.
Playing the original games with these suggested "enhancements" that break one of the key elements that seperates them from their predecessors. Pokemon Red with better graphics and music is simply an unbalanced and glitchy FireRed version. Silver or Crystal with better graphics and music still pales in comparison with their Nintendo DS remakes due to the more balanced gameplay, better battle mechanics, and compatibility with current generations. The other appeal is the ability to play these games on the limited vintage hardware.
Yes, Gameboy (Color) games can be emualted on the Nintendo DS and many other devices. However, the Nintendo DS does not have the complete iteration of the Z80 processor, and currently emulation cannot correctly emulate the WAV and noise sound channels. Even with "enhancements," no emulator in its current state could support these extra resources you would program. Extra room in the ROM and RAM for art, as well as more channels for music, are not feasible. Someone would have to program an emulator that could support these elements, and most Gameboy emulator developers have no desire to expand upon the original device's abilities.
If you want to play the games original RBY games in color similar to Yellow's palette: go get an N64, a transfer pack, original GB game, and Pokemon Stadium. The Gameboy Tower has natural color enhancements similar to those in the Yellow ROM. Hell, it can even be emulated. However, getting an emulator to play nice the the transfer pack function is a little tough. Get your toes wet with that if you must.
tl;dr If you are not familiar with disassembly, the Z80, or assembly language I strongly advise you shut your mouth and play Pokemon FireRed/SoulSilver or what have you. I hope you still enjoy Pokemon despite how it looks or sounds.