A method for colorimetric detection of a nucleic acid amplification reaction product in a sample, the method comprising: contacting the sample with a reaction mix under conditions such that a nucleic acid amplification reaction occurs and produces a nucleic acid amplification reaction product if the sample contains a target nucleic acid template molecule, the reaction mix having a starting pH and comprising: a buffer having a buffering capacity equivalent to Tris buffer at a concentration between 1.5 mM-19 mM in a solution having a pH of 8.0; an enzyme for catalyzing the nucleic acid amplification reaction; and a halochromic colorimetric agent having a transition pH range between the starting pH of the reaction mix and an expected ending pH of the reaction mix, the expected ending pH of the reaction mix affected by the nucleic acid amplification reaction; wherein if the target nucleic acid template molecule is present, the nucleic acid amplification reaction shifts the starting pH of the reaction mix towards the expected ending pH of the reaction mix, thereby causing a detectable colorimetric change of the halochromic colorimetric agent, and thereby indicating the presence of the target nucleic acid, and wherein if the target nucleic acid template molecule is not present, the nucleic acid amplification reaction does not generate an adequate number of protons to sufficiently change the starting pH of the reaction mix to cause a detectable colorimetric change of the halochromic colorimetric agent, thereby indicating that the nucleic acid amplification reaction product has not been produced. contacting the sample with a reaction mix under conditions such that a nucleic acid amplification reaction occurs and produces a nucleic acid amplification reaction product if the sample contains a target nucleic acid template molecule, the reaction mix having a starting pH and comprising: a buffer having a buffering capacity equivalent to Tris buffer at a concentration between 1.5 mM-19 mM in a solution having a pH of 8.0; an enzyme for catalyzing the nucleic acid amplification reaction; and a halochromic colorimetric agent having a transition pH range between the starting pH of the reaction mix and an expected ending pH of the reaction mix, the expected ending pH of the reaction mix affected by the nucleic acid amplification reaction; a buffer having a buffering capacity equivalent to Tris buffer at a concentration between 1.5 mM-19 mM in a solution having a pH of 8.0; an enzyme for catalyzing the nucleic acid amplification reaction; and a halochromic colorimetric agent having a transition pH range between the starting pH of the reaction mix and an expected ending pH of the reaction mix, the expected ending pH of the reaction mix affected by the nucleic acid amplification reaction; wherein if the target nucleic acid template molecule is present, the nucleic acid amplification reaction shifts the starting pH of the reaction mix towards the expected ending pH of the reaction mix, thereby causing a detectable colorimetric change of the halochromic colorimetric agent, and thereby indicating the presence of the target nucleic acid, and wherein if the target nucleic acid template molecule is not present, the nucleic acid amplification reaction does not generate an adequate number of protons to sufficiently change the starting pH of the reaction mix to cause a detectable colorimetric change of the halochromic colorimetric agent, thereby indicating that the nucleic acid amplification reaction product has not been produced. <EOS>