Identify looks the sequence up by exact checksum in UniParc — instant, and it needs nothing from you. BLAST is the fallback for a sequence that is not an exact UniProt entry; the EBI requires an email address for BLAST jobs and it is sent to them, so type it in yourself:
Paste sequences to begin
FASTA goes in the panel on the left. Two sequences are aligned for you with Needleman–Wunsch; three or more must already be aligned.
WW
Identical — shaded red.
IV
Substitution scoring +3, at or above the threshold — shaded orange.
PQ
Substitution scoring −1, below the threshold — left unmarked, as are gaps.
The example is the DOA/CLK2 alignment from McQuarrie DWJ, Bian W & Soller M (2024), bioRxiv 2024.11.25.625202, whose Supplementary Fig. 1 this colour scheme reproduces.