blue fish gone red
 

my blue betta is no longer totally blue, his fins are now almost totally red!?..help please

It's probably not a problem. Bettas often change colour for a number of reasons:

temperature
stress
becoming more comfortable in their environment
when they are happy and active
when they are unwell

Does he seem otherwise happy and healthy? How long have you had him? What is the temperature of the tank? Water parameters? Initially I wouldn't worry, but if you can answer these questions it'll help us better identify the reason.

blue fish gone red
 

well, i hav had him for about a month, but he seems a little down for the past few days, he is not at active as my other betta ie. not swimming around as much, but he is eating as he normally does, also he is leaning to his side alot when he is settling at the bottom of the tank(something he was not doin before). i hav to get a bigger acquarium for the both fishes, when i bought them though the salespersons told me nothing about checking the parameters neither did they tell me that they needed a filter and heater.they normally have them in tiny containers in the store so we believe they dont need much..guess this is not so. the only thing they sold me extra was the salt to take the chlorine out of the water but i know now that this is not enough..

Salt is not needed at all for FW fish unless treating for white spot (ich). It really annoys me how many lfs's will sell salt for this reason. To take the chlorine out of the water you can either add dechlorinator or let the water sit for a few hours for it to evaporate, HOWEVER, most water supplies also add chloramine, in which case it won't evaporate and dechlorinator is needed anyway. The dechlorinator also removes any metals in the water so really this is the nly way to be sure.